The gold cartrigde and the grey. They are both the same game, just a different casing. I have beat it a few times. The Games do not actually belong to me, my mom was the one that actually baught them, so I can not sell them, sorry.
As for finding used games, try your local pawn shops and yard/garage/estate sales. That is where I go to get games for my NES... also Fred Meyers (a department store round my parts) has started carrying Genisis, SNES and NES games. Though the selection is not very good at the store, pawns shops and yard/garage/estate sales will often times have a good selection.
Now the thing that is difficult to find is the map that originally came with the game... You can find copies online, but it is not the same...