Your are better off getting something like this. Way more useful. https://www.amazon.com/dp/B004MDXS0U?ref=ppx_pop_mob_ap_share
I used this inverter during Texas power outage for my regular plug in charger on my chromebook. https://www.amazon.com/BESTEK-300W-Power-Inverter-Adapter/dp/B004MDXS0U/ref=sxin_10_ac_d_pm?ac_md=1-0-VW5kZXIgJDUw-ac_d_pm&cv_ct_cx=inverter&dchild=1&keywords=inverter&pd_rd_i=B004MDXS0U&pd_rd_r=3f565ecd-0838-4eb2-800e-c4848820454c&pd_rd_w=aZv4m&pd_rd_wg=KZFxt&pf_rd_p=1996aa5c-bfb7-40b7-b677-a9bfb33f2c53&pf_rd_r=25CC2EZ6ZMM0PHPR3SCY&psc=1&qid=1617712416&sr=1-1-22d05c05-1231-4126-b7c4-3e7a9c0027d0
According to the box it requires 35W of power. Assume 10% loss from an inverter such as this one:
You'd need about 39 W to run this thing. You'll want a 12V power source. A deep cycle marine/RV battery would be good if you are able to bring one to your crab feed. You might see 1000 W-h from one, in which case it will keep your butter crockpot running for almost an entire day. If you want to bring a smaller battery you can, you could even bring 10 1.2V AA sized NiMH batteries if you wire them all together.
Okay - you have a car, a hybrid. Fine.
Most people are not particularly productive in coffee shops. They may be fun and social but not productive. Some stores get cranky about you holding down a table for long periods.
Either a separate hotspot (I use a Netgear Nighthawk 5G) or phone-as-hotspot (I use an iPhone 12 mini) work fine in most places. You'll do best with carrier diversity (say AT&T on one device and Verizon on the other).
There is no reason you can't charge off a hybrid. Some but not all cars both ICE, Hybrid, and EV turn off the power points when the car is off but that doesn't have anything to do with propulsion. I charge stuff off my Accord Hybrid all the time. Your best bet (<- opinion) is a 12V start battery just like the one in your car in parallel with the standard battery and a relay that charges that battery when the car is on and isolates it when the car is off. Any RV, marine, or snow plow dealer can help you. If you're near Annapolis MD I can help you.
You need more water. You should have at least one gallon per person per day. I like the Sceptre 5 gal "Jerry" jugs you can get at sporting goods stores, RV outlets, and marine stores. Get a jiggler like https://www.amazon.com/Siphon-Original-Safety-Grade-Valve/dp/B01N5MTGQS/ so you don't have to to pour water into a cup. You can buy water in 1, 2, and 5 gallon containers, but refilling your own is easier and more efficient.
Get the auto/air adapter for your laptop so you can charge off 12VDC.
Get a small inverter like this https://www.amazon.com/BESTEK-300W-Power-Inverter-Adapter/dp/B004MDXS0U/ (I have two of these for various applications). Note that you can only draw 6A from a cigarette lighter plug continuously, so 72W. You want a slightly bigger inverter for surges and to keep it from overheating.
Pen sized LED flashlight. Blue tape. Small tools. Small USB powered fan. Powered USB hub (get one that is 12VDC on the hub side of the wall wart).
I bought this car charger for Roo last year when we were using an air mattress and it has come in handy for countless things since then too. Definitely worth it to keep in your car just in case.
I'm not questioning your technique at all...some bikes take to bump starting better than others.
Two things wrong with your battery solution: 1) You're spending $60 to avoid removing the fairing to get to the battery. I imagine getting down to the battery, even on a Ducati, can't take you more than an hour. If you make more than $60/hour then it's well worth it, otherwise just pull the battery. 2) I'm not an electrical engineer kinda guy but at 12V that portable battery pumps out just over 3A. Your battery probably has more than 3A of juice in it right now which means it'll actually try to charge the portable battery rather than the other way around. If your battery was completely dead, the portable battery would only provide 3A...which isn't enough to start the bike.
Bottom line, remove the battery or get an extension cord and plug your tender in.
Alternatively, if you have a car get a power inverter and use that to plug your battery charger in.
I have one of these, and it works like a charm:
https://www.amazon.com/BESTEK-300W-Power-Inverter-Adapter/dp/B004MDXS0U
So everything below is something I have purchased myself and used. Background: I've worked mostly for cable companies and as a fiber optic lineman so I'm outside a lot and often in isolated areas.
I've started using these for water as opposed to traditional hard canteens. I do still use two quart plastic canteens for most of my water.
Good cheap backup knife, the bright red makes it hard to lose.
Bright small glowsticks, use them to mark people, places, and things.
Backup battery to charge my phone and whatnot.
A large pouch to hold whatever. I keep a couple changes of clothes in one. Food in another, and other stuff in a couple others.
Medium sized pouches.
Large-ish pouch, perfect size for the first aid kit I carry.
Reusable zipties.
A cheap flashlight.
A decent poncho.
Towels, because you're going to get wet and/or dirty.
First aid kit, because boo boos happen.
Knee pads, because sometimes you might have to crawl.
A belt that can hold pouches which can hold other supplies.
Tags that can tell others your blood type in case you can't.
An inverter for your vehicle so you can trade gas for juice.
Something to store matches or other small things you need to keep dry.
A good hammock to sleep in.
Something to cut things with.
A good small multi use screwdriver.
A backpack to carry stuff. This goes everywhere with me and holds enough to keep me going for a day or two.
We got this one for exactly that purpose, so I could work on road trips from the passenger seat. We’ve had it since October in a couple of cars and only use it when the car is running and it works great.
BESTEK 300W Power Inverter DC 12V... https://www.amazon.com/dp/B004MDXS0U?ref=ppx_pop_mob_ap_share
I'm using this inverter. Nothing crazy, just to charge laptops.
I just bought one of these (link below) and pump in the car. Definitely get the pump part wipes and wet bags to keep your parts in.
BESTEK 300W Power Inverter DC 12V to 110V AC Car Inverter with 4.2A Dual USB Car Adapter https://www.amazon.com/dp/B004MDXS0U/ref=cm_sw_r_cp_api_i_FAXF1CAJ74FD8C4KYYN6