Thanks, guys. I was thinking about getting a sheet of rigid insulation and gluing that to the door and then putting whiteboard or plexi on top of that. I have to say getting plain melamine board looks to be the cheapest route, but I don't know if it's solid melanmine (whiteboard) or melamine on particle board (i.e. cheap bookcase / desk material.) I'd be reluctant to go with cutting a white board if it were particle board or something like that underneath the plastic surface.