Brass tube would work I bet.
I just used the top of a bic pen innards. The area above where the ink is in that little tube. Fit over the brass pin like a glove and has a fat enough wall to hold against the compression when I drew in the pivot end tight.
Collarless pin because the ones I've seen were done either collarless or with the tiniest collars I've ever seen. Just looks better to me..
Good to know they can withstand s thinner profile Mike. There's a knot swirl on these down at the wedge end and. Just didn't wanna risk it..