Britain:
The 912E and 911 cables are different, and, as you know the 912E cable is getting hard to find. Try
www.masterautoparts.com and search part: POR039773
I have no affiliation with them, but ordered once and was very pleased. Be prepared for a high price, as these particular cables have always been expensive compared to all the other Porsche clutch cables.
Good luck,
Bill.