I assume based on the supported carts you need one with an SD card, not a flashcart that doesn't use one? Shame, but fair enough. Hopefully will get it when I have that type then. Very reasonable price considering the SP would be perfect for music/podcasts and if you want something like the Play-Yan it is ridiculously expensive, and manually using something like Meteo-AVI-to-GBA is a nightmare and can get barely any songs on it.
How many minutes/hours of content can it hold in theory?
Great work dude.