[The Mekon (John Briggs)]

Does anyone know if these knobs - common to Vixen mounts and focusers are available?
I have an old Custom 60M which must have spent too long in a sunny spot. The focuser knobs and the azimuth knob have all cracked.
If I cannot buy new ones, I may have to machine up some aluminium, but I would like to keep original.
Thanks