If I wasn't already hooked up with a Duo-RX and a TG-16 (just lacking a SuperGrafx), I'd probably look here on the board. Seems like just about everybody offers nice condition stuff at fair prices.
My Duo-RX came from a Japan Yahoo auction, though. I don't have any idea how much they're going for on there these days, but maybe it's worth looking into? The value of the yen recently dropped, so that helps. Although I had an unfair advantage in that my fiance bought it for me with the help of a friend with a personal middleman, so I don't think he paid middleman fees at all.