Amazon.com: Gamecube Adapter for Nintendo Switch Gamecube Controller Adapter and WII U and PC, Super Smash Bros Gamecube Controller Adapter. Support Turbo and Vibration Features with 180cm Long Cable : Video Games
Amazon.com: 4 Controllers for Gamecube,with 4 Extension Cables and 4-Port USB Adapter for Switch PC Wii U Console (BPOS) : Video Games
Just Got One of Those Gamecube Controllers That Plug Into the Wii Remote. What's the Difference Between These and the Actual Gamecube Controllers? : r/smashbros
raphnet. - Gamecube controller to Wiimote adapter
raphnet. - Classic controller to Gamecube/Wii adapter