Good spot Kong, I always wanted a screwy gondola but could never fabricate one myself (I fear taps and dies). What about this bad boy:

I've never owned a tap and die set. Since I work in relatively soft materials, I consider all screws self-tapping, given a hole that's the correct size and a bit of finesse.

What's interesting about the black holder is the tapered front will center the pen and keep it from wobbling. It also limits what pen can poke through the front, unfortunately. Also, people limited to drawing on perfectly vertical surfaces might need to tilt the pen, which this holder wouldn't allow.

Since I have a 3D printer right next to me, it's been pure laziness that I haven't designed and printed my dream gondola, or specific gondolas for different tasks. My handmade one has proven adequate in most situations, but lately I've been trying experiments that have the gondola pass over the same areas repeatedly, rubbing the ink too many times. I need to lift the stabilizing plate off the paper, perhaps with three plastic hemispheres glued near the edges of the paper-facing side of the plate. I'd try cap nuts, but I'm afraid the steel would be like silverpoint on some of the papers/surfaces I've been using. I'm also concerned that the lifting thingies would have a tendency to snag on the edges of the paper. Gotta experiment.