Amazon.com: Adafruit Nunchucky (Wii Nunchuck Breakout Adapter) [ADA345] : Video Games
Wii Nunchuck Controller Motion Plus Werleo Built-in 2 in 1 Remote Motion Nunchuck Controller with Silicon Case Compatible Nintendo Wii and Wii U & PC (Need Adapter) - Newegg.com
Wireless Wii nunchuk adapter frees you from cabled bondage
MOD-Wii-UEXT-NUNCHUCK - Open Source Hardware Board