Have you tired making one? Some cardboard to make a template, then cut it out of thin plywood and cover it with vinyl and foam, talk to www.seadooupholstery.com, he can send you the foam and vinyl..Just a suggestion...
Its not totally flat. Wood id out of the questions. It is curved and contoured. Someone here recently said they were going to try it with plexiglass I think by heating it up and molding it up. Hopefully they try it over the winter.