The Oxford Synthesizer Company OSCar is a marvelous synth, plagued by a less than great mechanical design.
As with many old synths, the pots start giving up after 30-40 years and finding exact replacements has been very difficult.
We have managed to get hold of a supply of New Old Stock pots from the original brand.
They are the same exact footprint and value, the only difference is that the pot shaft is 5 mm shorter than the originals.
We solved that by just super-gluing a 5 mm spacer on top of the pot. This makes no practical difference, the knobs grip on to the shaft in the lower end anyway.
The rotary switches are not available. We'll keep looking!
We don't have the actual plastic knobs or any other OSCar parts.