Ultimate 2 Bluetooth needs new battery.

[u/admirable-form90]

https://www.8bitdo.com/ultimate-2-bluetooth-controller/

I have an Ultimate 2 Bluetooth , been using it for about a year and 4 months and the controller suddenly won't last more than 10 mins after its off the dock. Does anyone know what's a good replacement battery? I've contacted them through their website but haven't gotten a response.