Numina;

I know this might not be a solution for you, but have you
thought about casting (making repro's) some new knobs? Take one of
your current (stock, correct) knobs, encapsulate this in silicone
rubber. Remove master knob once silicone has cured, then pour
castable urethane into the mold cavity and cure under pressure. If
you cast your urethane plastic in color you can match your original
knobs exactly. Just a thought for a DIY solution. I will keep an eye
out for stock knobs.

epitaph68