Get a small Game Boy for a smallish price
The Game Boy Micro is pretty much obsolete, outpaced by the DS and DS Lite in functionality. But the DS has yet to catch up in the "being ridiculously tiny" department, and lacks the important "being in the Nintendo Famicom controller color scheme" feature that one edition of the Micro offers.
Play-Asia is offering the Japanese Famicom edition of the Game Boy Micro for $60 this week, marked down from their usual price of $100. This may be just the thing if you want to be able to play It's Mr. Pants, but your actual pants are too tight for a DS Lite.