I have a Just Kampers cover. Whilset I am happy that it's protecting Jog, I would say it's a bit of a tight squeeze. If you look at photos of the cover on a VW, it's quite baggy on the van. With the commer, it's a bit of a tight fit, and I already have holes in it where the cover is tight on the rear edge of the pop up roof on the Wanderer, and it's worn some holes. However, it is cheaper than the one Jon recommend, and some cover is better than no cover.
A wandering commer blog - http://commerblog.wordpress.com/