We made covers at home from Sunbrella material I bought online. I also replaced the grills on our camper. I was not a fan of the twist locks the factory had installed so I purchased a section of awning
rail and used it for the top connection point. The cloth has a piece of hard plastic tubing sewn inside a pocket that then slides into the channel on the rail. I used industrial velcro on the other three sides. So far it has worked great, as you can see we also crafted a cover for the side vent too. I felt it was just as likely to get water in it while traveling in the rain.