http://www.angela.com/catalog/guitar-amp-parts/knobs.html
http://www.daviesmolding.com/standard-products/plastic-knobs/pointer-control/default.html
http://www.fliptops.net/catalog/index.php?cPath=29_31
http://www.banzaieffects.com/Plastic-c-323-p-2.html
I think JLM Audio used these knobs too…
Yes : http://www.jlmaudio.com/VMP2.htm