Keith and Steve, thanks for the ideas. Keith, my one big concern is that I am not nearly as good a welder as you are. Steve, I looked at that link, and what bothers me is that you can't tell what size the trailer body is. I don't see any specs at all, and the particular one you've pointed out seems to be the newer, wider model that my TJ just can't handle. But I like the idea!
I was talking with Scott Taylor yesterday (no, he did not fall off the planet). He suggested that I make the box frame myself, the have some sheet metal precisely cut and welded for the skin. It could then by bed lined for a finished look.