Oddly enough, they flew off the shelf and into my shopping cart, in the Auto Section at my local Safeway Store, while I was shopping for guacamole. They are a brand called "Helping Hand", from HBC Home & Hardware Products, Cranbury, NJ 08512. Made in USA, too!
Now, I have re-used the regular (not re-useable) ones, by slipping a #11 blade in there and prying up the locking lever gizmo. But these have a bit bulkier lock mechanism, with a thumb button to pry that lever gizmo up out of the ratchet track. Might work well for the rear end of tuned pipes, I'm thinkin'. Or at least useful for keeping the smoke tubes (aka "wires") up out of the way on something or other.
Steve