There IS a USB gamecube controller adaptor. Check out the following link - I would assume you can use it with a wired gamepad or a wavebird.
http://www.lik-sang.com/info.php?category=76&products_id=2143¬e: for some reason the site seems quite slow right now....let it load if you want to see the picture
PHeeNIxx
This comment was edited on Apr 12, 09:33.