You mean the Cruise Control stalk on the steering column? It is part of a 3-stalk switch and not available separately as a replacement.
The PN # is 996.613.219.00 . This includes the turnsignal indicator stalk, the wiper/washer stalk and the criuse control stalk. If you have the OEM computer w/ 4th stalk, that one stalk is removable and transferable to the new unit.
If buy new, check
Sunset Porsche in Oregon , for used, try
LA Porsche Dismantlers , or
Oklahoma Foreign
You'll also need a long T-30 Torx bit to remove the steering wheel to make the swap. Fairly easy. Should take less than 30 min.