I was at Fiberglass Unlimited in Clovis (Fresno) a while back and they had several sitting up in their rafters--I think rails that they have removed from Sanger mini cruisers that they have redone. I had never had one before and was considering taking it off. When I asked Manny about it, he suggested I leave it on, and I'm glad I did--it does come in handy. I got the impression that they were just extras hanging up out of the way, so you might be able to get one and modify it cheaper than building new.
Manny and Vito, owners, got started laying up boats at Sanger in the 60s, are great guys, and do good fiberglass work. Might be worth it to give them a call, they would probably know if what they have would work for your carrera--Fiberglass Unlimited, (559) 299-8826. Might also have a suggestion on where to have one fabricated.