Sega Genesis controller adapter for the GameCube?

[Leo_A]

I know these products exist to adapt 8/16 controllers for use on the GameCube/Wii, but could someone recommend one that works well and can still be easily bought (Some of these are now out of production and hard to find now)?

Edit: Or a SuperNes adapter that works well would be fine as well. Looking for something to pair a Genesis or SuperNes arcade stick to my Game Boy Player for arcade style games since I'm sick of moving my SuperNes Retroport back and forth between it and the Wii. I'd love another RetroZone SuperNes Retroport adapter, but they're unavailable now.