I have just retro fitted cruise control stalk part no 997.613.261.00.01C, but you need the wiring harness to connect the two stalks together, cruise to wiper, wiring harness part no 997.662.674.00
I have just done this retro fit today and will have it coded by my local OPC $tealer (UK) next Tue.
After reconnecting the battery, turn key (still in situ during retro fit) from Pos 0 to Pos 1 and wait 30 seconds to allow Throttle Learning, DO NOT press any foot pedals
Windows up and down to reset onetouch
Steering calibration. Drive forward with steering at 20 degree angle.