Raphnet makes an adapter cable that converts a classic controller (Wii classic, Wii classic pro, NES classic, SNES classic) into a GameCube port. If you can't stomach paying $200 for the Hori
raphnet. - Dual NES controller to USB adapter - V2
raphnet Classic controller USB conversion adapter V3 | eBay
raphnet. - Classic controller to USB adapter - V2
Input lag tests using SNES Classic controller + Raphnet low-latency USB adapter : r/emulation
raphnet technologies (@raphnet_tech) / Twitter
Amazon.com: Retro-Bit Tribute 64 2.4 GHz Wireless Controller V2 for Nintendo 64 (N64), Switch, PC, MacOS, RetroPie, Raspberry Pi and Other USB Devices (Atomic Purple) : Video Games
Amazon.com: Raphnet-tech
SNES / NES to Gamecube Controller Adapter Nintendo Wii Switch - Etsy Denmark
raphnet. - Classic controller to USB adapter - V2
raphnet. - Dual Classic controller to USB adapter - V2
raphnet] Neo Geo controller to USB adapter | eBay
Dreamcast Controller to USB adapter - V2 raphnet | eBay