For parts you can go to
www.sundolphinboats.com. They build the bulk of all paddleboats on the market from what I have seen and list parts online by model. As far as buying new boats, I see the Sun Dolphin boats for sale everywhere- some Walmarts (Farmington has them), Sam's Club, Sports Parafunalia in Gilford, etc. Mine came from Rochester Sports Center.
Good luck!