Hi Jacques, I searched around a couple yrs ago and found fiberglass seats by Necky and Dagger available for >$125, I'm not sure what's around now besides the add on cushions as mentioned in the Nantahala catalog. I would guess that you could get a plastic seat like in the whitewater boats from Perception but not sure if it would fit. $30 of Minicell would make a very cushy seat,especially with a thermarest seat pad thrown in. Homemade fiberglass seat will still cost about $50. CLC sells minicell,and a couple manufactured seats. what kind of kayak are you making?-lee