You're right it's gone. I can only find the bigger thicker battery with a different cover.
https://www.amazon.com/Perfine-10500mAh-Replacement-Li-Polymer-Protective/dp/B078HVK6ZP/

As for the 4100, give it time, I think this already happened and it came back.

1. Perfine BL-44E1F (Perfine LG V20 Extended Battery Perfine 10500mAh)
2. 10500 mAh
3. https://www.amazon.com/V20-Extended-Perfine10500mAh-BL-44E1F-Protective/dp/B078HVK6ZP (link was the first thing that came up on google, maybe /u/neoslover can confirm that this is the correct one)
4. $34.98
5. AccuBattery
6. NO temperature readout support according to this post

Conflicting reports see below