http://www.tapcoinc.com/
My dad works for a Soybean Processing Plant and i know when i was a kid in our garage we had a bunch of old grain elevator cups screwed to the wall for bolt storage bins.
The website above is a company that manufactures these. I don't know that they have any interest in selling 2 to 5 at a time as they normally sell them in lots of hundreds or thousands, but you may be able to contact them and see if they would send you a few for "Testing" or demonstration purposes. I cant seem to find anyone who sells these on the internet in any less than 100+ count minimum order @ 1 to 20 cents a piece, but they seem to be the same thing. If this is what carwash suppliers are buying and marking them up from 5 cents to $15, I want in on that gig.
Worth a shot if $15 from dultmeier sounds that unreasonable to you. They may send you 10 or 12 to test out in your "grain elevator" (car wash) if you ask nice.