Can't remember who, but someone here put in a nice van seat for the helm. Since there is not a seat mount in the C-Dory you have to match (mine was a piece of wood with 4 screws in it, you should be able to easily put in just about anything you want. You might check auto junk (sorry, dismantling) yards for late model seats. Probably a lot cheaper than "boat" seats.
Auto seats may not be as weather proof as a proper boat seat, but with the C-Dory the seats are pretty well sheltered from the weather.