I have a Supercard SD and I sometimes use it in my GBA Micro. It has great compatiability (it's played every game I threw at it) and allows you to do real time saves and use cheats. It does stick out of the Micro a bit but no more than it does with the original DS. Also it has the ability use up to 4gb SD cards. It also has built in emulators for gameboy, gameboy color, and NES so you can just put your roms on the memory chip and play them with out converting. Although you still need to convert the gba games.
I guess I don't follow so well considering what I hardware I have, but doesn't really ALL of them work with the Micro aside from things like the Flash2Advance USB considering it has to go into a standard GBA comms port only the GBA and SP have. I got a famicom micro and a nes style sp and have to use the NES one to load my card when I decide to dust it off.