Price-wise, I've heard that MetalMast in CT is hard to beat. But transporting a mast from afar is likely to add to your costs considerably. If you can locate a source neaby, all the better.
One fairly near source that comes to mind is Irvington Marina; they used to provide rigs for a major manufacturer of sailboats before it folded some time ago and they still produce extrusions now. Email address is firstname.lastname@example.org
; or call 804 438 5113 and ask for Wylie.