AA Gameboy Pocket

The modified back I made lets you slip AA batteries and keep a flat battery pack. I am still tinkering with the battery case but even without the clip, it fits tight for me. I included the clip if you want to glue it on. 

The back of the original model has a rounded battery cover. I made the back thicker to then fit a flat battery cover. I think it keeps it looking original while adding only a bit more thickness to the grip.