You could probably pick up a cheap used one at game stores such as GameStop, EBGames or a few other game stores if you live in North America. I know GameStop and EBGames sells GBA games as well, so while you're there you could pick up a few games to play! Purchasing an SP online would be a great idea as well, I know people sell them all over the place such as eBay, Amazon, and DealExtreme (though with DealExtreme some things are OEM or fake so I would be careful if purchasing there, but the things there are pretty cheap and include free shipping).