There's one on Ebay right now. Not mine.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=017&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=270054558381&rd=1
However, it screws onto the shift lever. Only the earliest 911/912 levers are threaded.
I have one that slides on and attaches with set screws. NLA and I presume not that common. $75 + shipping. PM me if interested or let me know if Walmart is selling them for $20.
Sherwood