Yeah. I've looked, and I haven't had any more luck finding it than you have. In fact, I have found several MIDI that claim to be in FFA but I swear I can't remember them from the original game. It's as if people have been uploading music from a different version of FFA than the one we're used to.

I guess all I can say is, maybe try looking around for themes that sound similar. The rest of the Seiken Densetsu series (Secret of Mana) might help.