I've seen the control panels on ebay, but I really don't know how they'd connect to a TDI. For starters, the control on the TDI to select where you want the air to be blown is purely mechanical, when you turn the knob it moves bits of bent wire to open and close valves. The climate control system would use a servo of some sort to do this.
If anyone does know how to do it then please post, as I wouldn't mind having a go myself.