So... now that I got my "science" right... 6*AAA (3 in row each) would give you 2400mAh@3,6V, and they *should* fit into the battery compartment without modifying it too much (could probably be done in a way that AAs still fit also)... quickly calculating... 3600mAh@3,6V=11h playtime, then 2400mAh@3,6=7h,30min!!!
That's quite a bit better than the ~4h the 2*AA give

Maybe someone (I guess not me

h34r: ) should give it a try and build a nice adaptor
edit: if the bottom, and a little bit of the side facing the SD slot of the inside plastic of the battery compartment would be cut, than 6*AAA stacked diagonally (bee hive like) would very likely fit with a closed lit.
It would probably look a bit messy inside, but the outer appearance of the GP2X would be unchanged! And AAs would still work too.
Damn I need a 3D printer for rapid prototyping B)
Now if there was a changer that charges 6 AAA at the same time

Actually that reminds me of the Lynx I had... that beast needed 6 AAs and you couldn't really play very long either
