Thanks to all who responded. I checked my hometown phone book, and the woman at a photo supply store suggested that I look up one of the ads in the back of a photographic magazine. She said I'd be sure to fine one in Chicago, for instance that could do the job for something like 39¢ per unit.

Failing that, I think perhaps the musicians' union idea may be a good one, even though my experience with the Kansas City local AF of M hasn't been all that great.
Jim