I think you mean either Portholes, or Port lights
(some times spelled Portlites and sometime simply called Ports). If your C26 is a Catalina, Catalina is still in business and you may be buy some parts directly from them or their OEM suppliers. If your boat is a Cal 26 things get harder indeed. That said, very often the frames on portlights are reusable. You can often replace the lenses with Lexan or Plexiglass and on operable ports the gaskets are often available as well.