The Raphnet Wii Classic Controller to USB is the real del. It's seriously as good as a Wired Xbox 360 guitar. Legitimately buy one of these if you have a Wii Guitar.
Amazon.com: ELECOM Wii USB Adapter, Game Classic Controller/Classic Controller Pro, Only compatible with Windows PC 1m / 39 inch length (JC-W01UWH) : Video Games
raphnet. - Wusbmote: Wiimote accessory to USB adapter