ZedLabz GameCube controller adapter cable for Nintendo Wii U - USB converter lead for Super Smash Bros (Compatible with PC Dolphin emulator): Amazon.co.uk: PC & Video Games
How to use a real GameCube controller or a Wiimote in Dolphin
Amazon.com: Ortz Gamecube USB Controller Adapter for Wii U & PC - 4 Ports - Perfect for Super smash Bros - - Windows & Wii U Compatible - Works on Dolphin Emulator: Video Games
Dolphin Emulator Wii U Mac | Peatix
Wii U Emulator For PC [Windows 7/8/Linux/Mac OS X] Download from Emuzone.org - video Dailymotion
How to Use a GameCube Controller with Dolphin - Make Tech Easier