Here's a set of black aluminum flat-top control knobs that I bought for a project, but I'm going a different direction with the preamp so I don't need these. The large ones are 20mm in diameter (so, slightly larger than a normal knob) and the smaller ones are 17mm in diameter. Nicely made and light, so they won't add much weight to your bass.
$25 shipped, CONUS.
$25 shipped, CONUS.
