Here is a set of knobs that I had custom made for my Spector. I just ended up liking the look of black knobs on that bass better. Going from memory, these are made from maple and the bottom of the stack is rosewood. They fit normal 6mm shaft pots, 6/8mm on the stacked knob, and they all have metal set screws.
Here's how they look on all different types of wood. If you ask me, I think they look fantastic on a black bass!
__________________ Fuzzrocious Club #194
Brubaker Brute Squad #18
Spector Club #224 (USA NS-5MM, NS-2J)