Well, I didn't call any of the companies -- for one thing, when you're doing your web research at night, the companies aren't open, and calls like that from work are frowned on (though 800 numbers at least don't incur long distance charges).

But I contacted Mike Holmes at mugwumps.com, and he tells me those clamps are no longer manufactured, so it's harder and harder to find one. I did look at some instruments on eBay with an eye to scavenging (and may do so for tuners, another need I have), but nothing came to light readily.

Yes, I'm sure I could call or email Elderly or Stewmac and perhaps find one, and I may do that, now that I have the leisure from having made my own. I may also just try to make a nicer one from hardware items. The design is simple, with only one sort-of-hard-to-find item (the proper nut for these things is really a hollow tube with threads that screws onto a bolt -- those familiar with office equipment and ledger binders may recognize a "Chicago Bolt" if I use that term) that can be substituted for if needs be.

In fact, if they turn out to be easy to find the makings of, I may fashion a half-dozen and sell them on the hard-to-find-banjo-items list.

Bob