I believe they stopped making boats in the late 90s. A seat should be
pretty easy to get, you'll need the distance between the runner
centres, the rigger was a little unusual and unless you get lucky by
finding a damaged boat will be difficult to find.
Latanzo has a lot of parts at reasonable prices, and may have made the OEM
parts:
http://latanzorowingparts.com/
Email him about the riggers