Try these links:
http://www.graphicsdirect.co.uk/subcategories/1002/evolution-double-action.htm
http://www.goldstarstockists.com/therest/revell-airbrush.htm
http://www.mainlytrains.com/acatalog/by-badger.html
http://www.shesto.co.uk/acatalog/Shesto_Catalogue_AIRBRUSHES_7.html
My advice would be go for something solid like a Badger 200 which is what I started with. It's a great brush to learn the basics on, and it'll last forever.
Karl