Have you tried DIB in Maryland? They gave me a very reasonable quote for a set of 733 tubes 18 months ago..here's a link: http://www.dibboats.com/
Also, I had a very poor experience with a well known UK tube maker when I ordered tubes for a larger RIB to be shipped to the US - but I think the problems would have been avoided if they were local so don't want to put the name here - they have an otherwise excellant reputation. But if you want the details pm me and I'll share the experience so you might avoid any similar problems. best of luck....