Battery type is 284449, meaning the battery is 2.8mm thick and 44mm by 49mm long/wide. Capacity 2.1Wh

Those are tricky to find, but any 2.8mm battery should fit if doesn't exceed the size. For example a slightly shorter TL284443 fits perfectly

YEEY!! We love pull tabs! Just pull them down to detach the battery

Here is the battery connector. To disconnect the battery simply pull the connector "up"

The battery connector is very fragile, try to take extra care while disconnecting the old battery