See also What to get a replacement battery?

I did not find a direct replacement identical battery on the market. I bought a battery for $6 on eBay.

My considerations: The voltage is 3.7V. The storage is at least 900mAh. The mechanical dimensions have to fit inside the compartment. And I selected a two-wire battery because I'm not understanding what the third wire is for so I'm keeping the old power control board and ribbon cable.

There is also a consideration of mass, that needs to match also. I found my new battery with larger dimensions was actually lighter. I will show how to add mass.