I read good reviews on 70mai Pro plus A500, with front and back camera for $100 on Amazon:

https://www.amazon.com/70mai-Camera-Built-IMX335-Android/dp/B08TBNFG66

Don't buy now though -- they run frequent promotion with $20 discount. Wait for that.

I personally bought one and plan to use it on mine (still waiting!) .

Currently I am using it on my commute car and it performs well. The only concern is it's a fully enclosed body with no ventilation holes. I live in houston so heat might be an issue (or not).

It does run on battery -- but it's not soldered and battery is widely available and easily replaceable.