Sorry you have received no reply from the States. I thought that they may have been at NEAF http://www.rocklandastronomy.com/NEAF/Index.html but they do not seem to be on the vendors list.
Looking in my Metal.plastic and Motors file you could try this UK supplier , particularly their Nylon Screws http://www.modelfixings.co.uk/nylon_screws.htm
Hope you can find something that fits (they do small quantities). It could be metric or UNC threaded.