Photo: Watch Impress
Japanese GameTech offers a manual charger for the Nintendo DS.
Cranking the small charger for about 3 minutes gives 20 minutes play-time. So you are just close to the high-score and then th charge is drained again unless you crank the little handle. Maybe it is better to get a couple of spare batteries. The gadget also works with the Gameboy Advance SP.
More details on Joystiq.
Check out this Nintendo DS Bundle on Amazon.com.