Try Handcraft Mattress Company in Ft. Lauderdale. They are the original supplier for Sea Ray. We just had a 9" made for our 01 460 Dancer and we love it.
With the dryer running, check how much air is coming out of the vent on the side of the boat. Like others have said, check the vent line. Mine was clogged. Also, it's a fire hazard. Good luck.