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.

My battery when the phone was new wasn't lasting even a full day (and I'm a light phone user). I replaced the battery with a Shenmz 4380mAh battery from Amazon and it then would last 2-3 days easily. I never charged more than every other day.

Amazon US says it's currently unavailable, but maybe you'll have better luck finding it in Canada. It's the same thickness as the original battery, so there's no problem with it fitting in the standard case.

https://www.amazon.com/SHENMZ-Upgraded-Replacement-BL-44E1F-Extended/dp/B08KSTYGXM