Can't give you a particular merchant's named, but, I had the door window on my Damon Tuscany MH fog up, and of course in cold weather that turns to a lot of frost. I took it to a local glass door and window shop. They separated the panes, cleaned them and resealed them. The door has been good for more that a year. Good luck with your window.
2007 Damon Tuscany 4072
Brian & Wendy