I don't know if you need a vintage sheave, but I bought this reproduction sheave on ebay from taiwan. LINK
I fit mine on a worksman rear wheel with 11gauge spokes. I don't think the hardware was meant for that large of spokes, so I filed the grooves out a little larger with a small round file. It fits well, I have not broke any spokes and it has worked flawlessly for almost two years now.