I've thought about this myself, but never wanted to spend the money on something that might not work. Right now I have one 8GB, 2 4GB, and a 1GB Pro Duo card. I went to a second-hand game store, and bought them there. The 8GB card was $40, which was why I bought it. Normally, they're a bit more than that. If you do end up getting it, and it works, please let me know, because I have a lot of Micro SD cards, too.
PS: I have every game every released as either an iso or a cso, so if you want anything, PM me.