I have an Audere 3ZB preamp and a set of knobs for sale.
The 3ZB has volume, blend, high mid, low mid, and stacked treble bass.
The knobs are one of these:
with two more of the top parts (so two mini knobs and one stacked mini set)
and two knobs like the black one in this pic:
You'll have to rewire the preamp to the jack, since I connected it to the original jack in my bass when I installed it. I'd be happy to do this for you as well. The preamp is currently set up for 9v operation but I could make it 18v if needed.
All for $180 shipped CONUS. Paypal preferred.