I have seen the covers you talk about. They must be custom made, just like the screen fronts I've seen. Although a tonneau would be nice with a hatch, it wouldn't be much help with a huge hole opened up in it while towing. If you need to store equipment in the back while towing, check out some of the 5th wheel boxes. This site is just an example of what I'm talking about: http://www.800toolbox.com/5thwheel.htm
Just did a quick google search and this was the first link. As for the Retrax, you can check my pics. Shop around and you'll see, the Retrax is the best cover.