A little bit of electronic know-how is all it takes to turn your DS into a solar powered gaming device. Captain Planet would be proud.
This Instructable should guide you through all the steps necessary to make a recharging system. The four solar panels cannot provide enough juice for constant gaming, but just enough to trickle charge the battery when not in use. Really, the system isn’t that hard to construct with just a bit of soldering and hot gluing and with the DSi coming out soon, it could be a fun project without worring about bricking your DS gaming fun forever.