I stopped in at 84 boat works about a week ago. When I described what I wanted, the guy said flat out that it wasn't worth it for a RHIB that wasn't a Center console. His estimate was in line with the guy in Miami that I spoke to.
I have checked with several shops now. The average quote is about $3,500 for Orca tubes. Orca is the modern material that replaced Hypalon when the original manufacturer of Hypalon stopped making it. Apparently, Orca is pretty much a dead knockoff.
I had one guy tell me that he had a guy that could do tubes for $1,500, but I think he was talking about Vinyl, which I don't want. I think that I am going to try repairing the existing tubes. A few hundred bucks will get me several square feet of Orca, a box of rubber gloves, & a quart of Clifton Adhesive.