Look here
Seriously, I don’t quite understand this thread. Potentiometers are standardized and so are the knobs. (You can, btw, just tear them off upward. Gently but firm!) There are two or three different diameters for the spindles and every electronics shop in the world will provide a variety of knobs.
If you’re the adventurous or retro type, just look at pawn shops, attics, granny’s basement for old radios, TV sets and the like for knobs. I’ve seen a lot of really nice custom guitars with knobs from old devices…