I think I got 5 or 6 cr2032 battery's on ebay for something like 2 dollars
shipped . They are widlely used in car remotes and other small devices.
keyfob guy
https://www.bimmerfest.com/forums/sh...d.php?t=903551
https://www.bimmerfest.com/forums/sh...d.php?t=874226
https://www.facebook.com/GcodingBMW