I think I got this Magic Mouse as a gift a few years back. Used it sporadically as the battery changes weren't really worth it (lasts about 2 months of daily use, with switching off).

This is a story of how two wrongs made a right. Or at least a hack.

Printed a hand support ( http://www.thingiverse.com/thing:455739 ) but my printer failed at the last cm of print so there was a gap next to empty space.

Lost a skid when I decided to clean it, and I replaced them with snipped pen cartridges. This exposed two gaps next to the battery cover.

I put two and two together, and decided that I should mod it to use a rechargable power source under the hand support, with all the necessary circuitry.