I too was wondering this same thing. My 4xxxmAh Perfine is starting to lose capacity and I wanted to purchase another one from Amazon, but I haven't seen it listed for several weeks.

Anyone have a recommendation for any of the other brands there on Amazon?

I was looking at the Wavypo: https://amazon.com/Wavypo-Battery-3500mAh-Replacement-Warranty/dp/B07QNPM24L

and the Shemez: https://amazon.com/dp/B08KSTYGXM/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B08KSTYGXM

But don't know anyone who used those Li-Po batteries on the V20.