So, I sincerely hope this is a simple enough question for people here. I have an R4 in my NDS Lite running with R4Wood, but there are some GBA games I want to be able to play on the go - without trying to figure out how to do more with the R4 itself. I'm looking for a Slot-2 cart with MicroSD support, preferably one that matches the form factor of the NDS Lite's dummy cartridge, so that I can either fit it comfortably in my travel case or pocket; but form factor's a minor concern over being able to easily handle GBA games with the R4Wood firmware.

Does anyone have any suggestions as to where I can find it for a reasonable cost?