Otherwise, all the other parts could be made from scratch in a local millwork shop. I'm not sure what would need steam bending besides those inside ribs, but steam bending is not that highly technical.
As for a used replacement, Google is your friend, but it may take a while. I own several boats which have turned out to be rare and unreplaceable. Just have to keep fixing them.
Sport Cases (Electronics)
Touring Kayak Paddles