I used a Targa Roof Switch (996 613 119 10 A05) which you can purchase from any dealer.

Just follow the wiring in pictures. You can see I joinded the 2 wires connected to the top plug.

NOTE: If you want the switch to light up like your other switches, move the plug on the left to the bottom center one. Run 2 wires from the side slots to the same side slots on the Power Window Switches. I made this change, but have yet to take pictures.