That's a great question and I'm curious to hear what's currently available.
I am in SoCal and have a 16' Cruiser. I'm actually looking for a Radar Arch, but never the less some stainless work. I talked to Tanner and Railmakers about getting one.
Tanner wasn't too interested as the 16' Cruiser hasn't been made for a while, sounded like they were pretty busy and not really setup to do any custom work right now.
Railmakers could do it but I would need to bring the boat up to Seattle so they could make a template.