You can use the Smash Brothers Gamecube adapter in portable mode with a USB C adapter (Rumble works too) : r/NintendoSwitch
GameCube Controller Adapter for Wii U and PC USB Two ports
USB-C to Gamecube Cable – 20XX
Eight Player GameCube Adapter Is Ready For Smash | Hackaday
GameCube Controller Adapter for Wii U, Nintendo Switch and PC USB – Lexuma
Switch Gamecube Controller Adapter, Super Smash Bros Gamecube Adapter for Nintendo Switch, Wii U and PC USB with 4 Ports - Plug & Play, No Drivers Needed Nintendo Wii U Systems - Newegg.com
Nyko Retro Controller Adapter Single 1- Port GameCube Controller Adapt – Gametronex.com
YEUHTLL 4 Ports Converter for GameCube GC Controller, USB Adapter Plug & Play for NS Switch NGC/Wii U/PC Star Fighting Games - Walmart.com
NEXiLUX Nintendo Switch GameCube Controller Adapter for Wii U, PC USB – J&L Video Games New York City
Gamecube USB Controller - Purple - for Windows, Mac, and Linux - by Mars Devices - Walmart.com
Classic Nintendo GC Gamecube Style USB Wired Controller Orange
Retro Link GameCube Style USB Wired Controller - Walmart.com
PS2 To PC (USB), Xbox, And Nintendo GameCube Controller Adapter Cord Cable RARE | eBay
Amazon.com: GameCube Controller Adapter for Wii U, PC USB & Switch - NEXiLUX : Video Games
GameCube Controller Adapter 4 Port Compatible with Nintendo Switch Wii U & PC USB
raphnet. - Gamecube to USB adapter - V3
Retro Controller Adapter for Nintendo Switch™ – Nyko Technologies
Amazon.com: GameCube Controller Adapter : Video Games
Amazon.com: 4 Controllers for Gamecube，with 4 Extension Cables and 4-Port USB Adapter for Switch PC Wii U Console (BBRG) : Video Games
GameCube Controller Adapter for Wii U, Nintendo Switch and PC USB by L
GameCube Controller Adapter | Switch GameCube Adapter
Amazon.com: CirKa Premium GameCube USB Controller for PC/ Mac (Black) : Video Games
PS2 To PC (USB), Xbox, And Nintendo GameCube Controller Adapter Cord Cable RARE | eBay
Switch Pro Controller USB-C to GameCube Cable - ProGCC | Hand Held Legend
