No personal experience with these, but the Swiss Gear brand on Amazon has excellent reviews and has sidewalls and screens available.  I think it's made from a 200 denier fabric, which is not super heavy, but doesn't weigh a ton either.  I know that bus depot also has larger awnings now, if you want to attach something to the van. I can certainly see the appeal of the shelter though, but they do take up a lot of space in an already cramped van.

Troy