Wii U can use two GameCube controller adapters
Mayflash GameCube Controller Adapter for Wii U and PC USB (4 Port) - Walmart.com
Mayflash GameCube Controller Adapter for Wii & Wii U (Dual Pack), White - Walmart.com
GameCube Controller Adapter for Wii U for Wii U
4-Port Controller Adapter for GameCube® Compatible with Nintendo Switch® / Wii U® / PC/ Mac®
GameCube Controller Adapter for Wii & Wii U (Dual Pack), White
GameCube Controller Adapter | Switch GameCube Adapter
raphnet. - Classic controller to Gamecube/Wii adapter
Classic controller to Gamecube/Wii adapter – (raphnet) – ASA College: Florida
Mayflash Dual Pack for GameCube GC Controller Adapter Converter for Wii for WiiU
Amazon.com: Mayflash GC Controller Adapter for Wii & Wii U (Dual Pack), White : Video Games
raphnet. - Gamecube controller to Wiimote adapter
Confirmed: The Wii U GameCube Controller Adapter will not work on DDR, Active Life, or Cyberbike | Gaming.Fit
GC Controller Adapter for Wii/Wii U (PLAY-ASIA.COM Edition) for Nintendo Wii, Wii U
Wii U Gamecube Adapter (Violet) for Windows, Wii U, Android
Amazon.com: Mayflash Nintendo GameCube Controller Adapter for Wii/Wii U : Video Games
Mayflash 4 Player GC Adapter for Switch / Wii U / PC
Amazon.com: Y Team Controller Adapter for Gamecube, Compatible with Nintendo Switch, Super Smash Bros Switch Gamecube Adapter for WII U/PC with 4 Port : Video Games
raphnet. - Classic controller to Gamecube/Wii adapter
Wii U 4 Port Gamecube Controller Adapter
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
GameCube Controller Adapter for Wii U, Nintendo Switch and PC USB by L
Amazon.com: Gamecube Controller Adapter for Switch/Switch OLED.Gamecube Adapter Compatible with PC Wii U.Adapter with 4 Ports 6 FT(1.8M) Cable Support Turbo and Vibration Features Super Smash Bros : Video Games
4 Ports GameCube Controller Adapter for Nintendo Wii U
GameCube Controller Adapter For Wii PC and Nintendo Switch
Does the USB to gamecube adapter work in Wii mode on the Wii U? : r/wiiu
