Where to get THRIFTAIR heater cable knob for '66?

[luvbowties]

Where do I get a heater cable knob for a '66 C-10 WITH THRIFT AIR? It holds onto cable for pulling to adjust temp./direction AND it also tightens onto the cable for twisting/rotating to alter fan speeds. It fits the type cable-and-switch like #12 on LMC's site: >>http://www.lmctruck.com/icatalog/cbe/full.aspx?Page=34 <<.

Thanks for all suggestions. I'm even open to an alternate-appearing knob, just in order to achieve functionality, at this point. Naturally, I prefer original looks. Mine works good, but looks like a Boston Bull chewed most of it off--without any plan on where he was going with the mod! [Nice dog, though!]

Sam