The makers of this unit are out of business. I did go to Guitar Center with a fader knob in my pocket. I tried it on several things but only the Mackie 32x8 came close. The knob fit on the fader stalk, but the faders knobs themselves are a little too big and only come in white (my faders are black).
Not that the color is a big deal, but there isn't a lot of room between my faders so I need something a little slimmer.
You need an electronics store, not a mucis shop. There are several of them just in Sweden, som I'm sure the US must have tons of them on-line. There you can buy faders and fader knobs by the truckload. And if you don't like one of the knobs having a different design, replace them all. They are cheap.