I realize this topic is getting a bit long in the tooth but I myself was considering the flash cart for a GB Micro I have or buying a pocket go, which is about $35. USD at the time of this writing. I have 56 original games and 2 translated ones; Binding Blade and Mother 3. I tried buying a Mother 3 cart to play on it and was assured it would play on anything that played GBA games, but to my chagrin, it did not play on the GB Micro but DID play on my GBA SP ( & DS Lite). I tried it on my friends micro with the same result. A few phone calls to a knowledgeable Nintendo (referred) tech got me an answer I didn't expect.
The GB Micro handles memory differently than the GBA SP. Remember, the Micro does not play GB/C games either. It is not simply because it doesn't fit either. SO, some Ebay sold reflashed cards won't work on it. I'm not certain if those are reflashed chips or aftermarket ones. There is something (I forgot their exact explanation, maybe they used less internal memory, considering the smaller form factor) about the manner in which the memory is handled, in the system, before it is actually run that is slightly different. I never mentioned to N that I was having trouble running an aftermarket Flashed GBA Cart.
Maybe it [that specific setup/chip/cart] required more memory than the system [MIcro] could offer for use? I've long forgotten... I always intended on posting a vid on this but I don't have a PC camera and really what's the purpose, who really cared besides me.
I know this seems off topic but I just watched a VID where the cart reacted diff. on his GBA SP than his MIcro, which reminded my of that problem.