If your talking about those silver ones with the blue around the edge, I'm absolutely positive there is an aussie company that makes them, but I can't remember their name for the life of me. I'm fairly certain that they're custom built for your aircraft, so if they have a website they may not advertise they do PA31, but they will advertise custom fitting, which could be done for you.
Sorry I can't remember the name, arrr damn mental blocks
