Thanks for the tips. I'ts actually been quite awhile since I've even searched for O2 stuff. I have an original boxed system & collection from my youth. Smithereens is one game that I fondly remember playing at a friends when the voice module first came out. Turtles is another one I could never locate back when I was trying to fill in my collection. The only others games I am missing are education titles that I would probably never play anyway: Keyboard Creations, S.I.D. the Spellbinder, Nimble Numbers Ned, Pachinko, and I've Got Your Number. I do have a mint boxed Killer Bees however, which I believe is pretty rare.
I always thought the O2 controllers were the best of these early systems and lasted a very long time through heavy play.
I don't understand why one would want to play an O2 with an NES or Genesis gamepad?