I have a few 6V air pumps available to the membership at $22. each, including shipping in U.S. E-mail me for more info.
These are similar to those used in Automatic Blood Pressure machines. If enough people are interested, I think I can get the 12V models. The pumps are used in the Recirculating Compressed Air Ballast System (RCABS), as described under 'Documents' on my site, Art Broder's Models. Also see a picture of the pumps on this site.