I use these, they work great.
https://www.amazon.com/YISHDA-2x3200mAh-Replacement-BL-44E1F-Warranty/dp/B0722S1T67/ref=sr_1_3?keywords=v20+battery+yishda&qid=1549745740&s=gateway&sr=8-3

Yes. Both the BCK-5200 Battery Charging Cradle (Charging via USB-C) and any given 2x Battery and Wall Cradle will work. I have both and I find both very useful. I have the White cradle mounted to the wall near my bed with a command strip, and I can just come home from work, pull the battery out and put the new one in. I use the wall cradle at work to charge a battery and my Sony WI-1000x headphones, becuase the wall cradle does actually have an additional USB port on the side. I find that charging the battery and something via the USB does take longer on both, so keep that in mind. I'd try and find a BCK-5200 on Ebay or Swappa or something and get that, and grab a wall cradle. You can put the wall cradle in your backpack or pocket on the way out the door and basically always have full battery, it's really nice. The same can be said for the BCK-5200 though - I occasionally would use it in the car to charge my second battery as well, or use a portable power bank. It's slimmer and nicer looking, and I could be mistaken but IIRC also support QC3.0 + PD, so it'll charge faster. /u/JeromeZilcher will be able to confirm that.

I've had a Yishda battery (bought the two-pack that came with a charger, lost the second battery within a month) for about a year now. Accubattery reports it as having something like 2700 mAh left. So, nothing spectacular IMO but I think it pretty closely resembles an OEM battery.

It definitely wasn't a lemon, and it was affordably priced.

Link: https://www.amazon.com/YISHDA-2x3200mAh-Replacement-BL-44E1F-Warranty/dp/B0722S1T67/

Sources/Notes to self

https://www.ifixit.com/Store/Parts/LG-V20-Replacement-Battery/IF357-004-1

https://www.amazon.com/Genuine-BL-44E1F-3080mAh-LG-Non-Retail/dp/B01MSESWO6/ref=sr_1_5?s=wireless&ie=UTF8&qid=1542827205&sr=1-5&keywords=lg+v20+battery

Offbrand

https://www.amazon.com/YISHDA-2x3200mAh-Replacement-BL-44E1F-Warranty/dp/B0722S1T67/ref=sr_1_6?s=wireless&ie=UTF8&qid=1542827205&sr=1-6&keywords=lg%2Bv20%2Bbattery&th=1

I'd prefer to get a spare OEM myself, but given the price straight from LG, (and all the apparent counterfeits floating around prevent me from looking at eBay and Amazon) I can't rationalize it when there are 2x battery kits with a charger that are cheaper.

I'd prefer an Anker, but they don't seem to make a battery for the V20. Not interested in ZeroLemon (bad experiences) and PowerBear doesn't sell a 2x+Charger kit, which leaves YISHDA and JUBOTY based on reviews (here and on Amazon). Which of these two should I go with? Has anybody bought and tried either/both of these?

https://www.amazon.com/Batteries-YISHDA-Replacement-Battery-BL-44E1F/dp/B0722S1T67/ https://www.amazon.com/Battery-JUBOTY-Replacement-BL-44E1F-Warranty/dp/B07BHFLM5V/