Shot in the Dark - 1970s Guyatone Pedal Knobs

This is definitely a shot in the Dark; I'm trying to source some of the knobs Guyatone used on their guitar pedals during the 1970s. They're a waisted design in black with a white position indicator stripe, a circular shaft and secured with a flathead grub screw.

I got a few off a dead pedal some years back and I'm really liking them as bass guitar control knobs but I can't seem to find anywhere to buy additional ones for my other guitars, short of buying 1970s pedals and stripping the knobs off them (NOT financially viable I'm sure you can imagine).

Anyone got any good leads on where I might find some?

Thanks