Graupner, APC, and Zinger all make them. Here are the search results from the Tower site, using the keyword "pusher".

http://www2.towerhobbies.com/cgi-bin...=++&search3=Go

Not an aerodynamics question, but I'd like to know who makes large (3" to 4" diameter) pusher SPINNERS. The only source I could find was that Tru-Turn would custom cut them for $9.50 each.