I am restoring a Mariner 19 and need to replace the two fixed ports. They are probably Plexiglas and they are held in place by a rubber gasket.Both the plexiglas and the gasket have deteriorated badly.The original gasket is black with a white center insert. I would settle for solid black or white and will cut out a new lexan or plexiglas port from a sheet of either material unless the whole assembly is available somewhere. Does anyone know where I can either buy the whole assemblies or at least the gasket material?