Battery packs are all dependent on how much you need, I find the smallest you can get away with is the best. Less to put in my backpack and charge at the library/panera/gym.
My personal fav is anything from the Anker brand, but there's a lot of good options out there. I currently use https://www.amazon.com/Anker-Portable-10000mAh-Delivery-PowerCore-dp-B08LH26PFT/dp/B08LH26PFT/
For fan, I got a cheaper one on sale but something like this works well https://www.amazon.com/10000mAh-Battery-Operated-Portable-Stroller/dp/B08866RDYK
To me the keys are
We have the Opolar brand, but it looks like it's no longer available on amazon. This guy appears to be similar, we love it though. Battery lasts two full days on Low and all night on High and it moves some serious air. It swivels 360 and up and down so you can clamp it to anything and aim it where ever you want. We are super happy with it
If you want to stay cool KOONIE 10000mAh Rechargeable... https://www.amazon.com/dp/B08866RDYK?ref=ppx_pop_mob_ap_share
Now that's an Amazon product image if I've ever seen one...
The fan I bought isn't available anymore but this one is probably the exact same under a different name.
The high setting is reasonably noisy but low and medium are very quiet.
I started being much more careful with dogs in the car after I saw the outcome of a loose dog ejected from a car after an accident. Seeing a dog sliding through the busy intersection was pretty traumatizing to me. As the dog got up and ran off I don't think it was real happy either.
I travel both long distance and around the town with dogs. I may be in a truck or a topless Jeep. I use a dog harness and these https://www.amazon.com/gp/product/B07ZYJGRBS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
Attach the tether to the harness NOT the dog collar. These tethers can either snap onto the hooks for a child car seat or clip into a seat belt. I cross tether when in the Jeep. They have a bungie in them so a quick stop is not painful but they are very strong.
We wear seat belts and so do our kids. It makes sense to secure the animals as well.
I also use these https://www.amazon.com/dp/B08866RDYK/?_encoding=UTF8&pd_rd_i=B08866RDYK&ref_=sbv_store_search&pd_rd_w=MjFTF&content-id=amzn1.sym.ffd1659e-da72-4e4c-88cd-2e6703ef80a3%3Aamzn1.sym.ffd1659e-da72-4e4c-88cd-2e6703ef80a3&pf_rd_p=ffd1659e-da72-4e4c-88cd-2e6703ef80a3&pf_rd_r=XBZS2M0YBMVXTRVHNR48&pd_rd_wg=mMHkh&pd_rd_r=17cb58c7-c059-41c6-9697-f77530a0b25f&&pd_rd_plhdr=t to keep some air flow. They are pretty powerful and USB chargeable and clip to just about anything.
Have fun and carry barf bags just in case. Don't ask how I know.
https://www.amazon.com/dp/B08866RDYK?psc=1&ref=ppx_yo2ov_dt_b_product_details
this is the best one in the world. i use it all the time. i have a swing arm attached to my bed and i use this fan on that. it also stands normally so i can have it anywhere. theres a smaller version from the same company if youd prefer.