I asked for one of these a while back and got no replies. Either not many sold or no one wants to parts with them!
I think I would make my own as well, not so much for the cost but because I could glue sound deadening foam/material onto the back of it as needed to get a nice shape if needed (and to stop the worst noise). I think I would have a go with this stuff: http://www.megavanmats.com/liningcarpet.htm