Its funny the places where you run into NYDave, the kilo booth, Indian restaurants and that store that specializes in midget porn...
Kilo makes a knob like that, although logic would suggest that any knob used on a M product is obviously copyrighted and you'll fall in a flaming ball of fire into the depths of hell if you use them on your DIY. There are similar knobs on the newer dbx stuff and I think the apogee uses purple ones.
Kilo did custom knobs for my console and they came out absolutely fabulous, kilo totally rules and the guys that run the place are totally top notch, cant reccomend them highly enough. You can order most of the standard kilo items at Digikey.
dave