I would recommend Don's Marine Salvage in Clearwater Florida.
Welcome to Don's Marine Salvage. Your new and used boat parts heaven!
I had to replace my boom after I got my boat back, and they sold me a new Dwyer boom with all the fittings for a lot less than I would have had to pay Dwyer for the extrusion alone.
I got it 2 days after it shipped.
Good service (but they close early on Friday), and easy to work with.
It's nice to be able to say good things about vendors, rather than having to warn people about the bad ones!