Have you checked Cabelas and the Sportsmensguide? I think I've seen the type of thing you're looking for in both of those catalogs!

After doing a lot more research since posting, I came up with this product which seems to fit the bill. All the others were massive tents off the back of the SUV rather than just something that 'tented' the tailgate.

http://www.xocom.com/ss/

Here is a link that might be useful: XO-Shell

Sherry3, Just today, I was out browsing the Pontiac Aztec because it has a tent option, factory made. Unfortunately, I learned that they have stopped making that vehicle. Your idea of an after market tent attached to the back looks like an even better idea. $300 dollars vs. $20,000! Thanks for the link.

Try the Campmore cataloge for tailgate tents.