I got my cover from here: http://www.boatcoversdirect.com/
Mine is a "custom" cover, cut and sized specifically for my model boat. They have one for yours too.
Several different fabrics available at different price points.
In my opinion though I'm not convinced that any cover is really "trailerable" - at least at higher speeds. Even though they might stay on the boat the covers just do not fit tightly enough to keep them from flapping around. If they do flap then they will wear quickly at the stress and hard points; like on the windshield frame.
If I just had to have the boat covered while towing at highway speeds I would use a mooring cover instead.