Bavarian sound werks sells one, as do Crutchfield and others.
Have a search in DIY and Sound / Audio, there are DIYs and more info on what you need to do.
I can help with
* Reading Codes / Coding your car
* R&R FCAs, Tie Rods, Sway links....
Need an RTAB tool? Or clutch fan and water pump tools? PM me.