Easy to make, even without a lathe.
David Barnett - SW Florida
>Use brass threaded rod, either drill and blind tap a shallow hole* in a bar of 360 brass (easy to work), tightly screw in threaded rod (bolt shank, all-thread, whatever), flux, hard (silver) solder just enough to run into the thread hole, a couple paillons is all you need, then use a half-round file to shape, finishing up with sandpaper. If you collar the base of the thumbscrew you can tap for more threads. Doesn't have to be round and the thumb part doesn't have to be an oval or ellipse. If you do want a rounded collar, then try turning it in a drill press using files WITH HANDLES (emphasis for safety) and eye protection. Dremel or Foredom tools with sanding drums can grind the relief in little time or you can use the top wheel of a 1" belt sander (contact wheel). If yours is hard plastic like mine was, a hard rubber caster contact wheel is an easy upgrade mod.
*My first one of these I drilled and tapped a hole through the entire chunk of brass (a bar is easier to manage, though -- just hacksaw off when you know how much you need and after you affix the threaded rod). You can use epoxy when there's this much thread. The epoxies for golf club making have incredible shear strength, btw.