I bought a spare for my F&S 3spd from Retrobikesupply on Ebay. I dont' know if they have more or not.
The threading on it is different the S/A. If you cant' find it online then you might try asking various LBS's. Or try over in Europe. Mine came off a Norweigen bike.
ADDED: I never tried it but you may ask if the new SRAM hubs might have part that works. From my understanding, The internals of haven' t changed much.
Last edited by cman; 08-04-08 at 09:51 AM.