Making a MIDI yourself is a bit of work, but then you are free to choose whatever song you want . When I was making my pick for PRC282 and was looking for existing MIDI files, the choices turned out to be more limited than I had thought.
I remember there used to be quite a lot more MIDIs of MSX games, but a lot of sites collecting and hosting them have shut down and the MIDI files were lost along with them. Two of the three MIDI files I provided for the PRC282 Illusion Theme were recovered from the archive.org way-back machine. Also many MIDI arrangements are too far from the original to be usable. So next time (I’m optimistic ;p) I think I’ll also have to bite the bullet and make one myself.
Though, I just received a MIDI-PAC today, which converts MSX YM2413 (OPLL) music to MIDI, that would be quite helpful there I imagine . It would be cool if emulators implemented similar functionality.