I purchased a cargo screen off eBay for $169. That included tax and shipping. I haven't needed to use it yet, so it is stored in it's designated place under the floor in the rear. The third row needs to be folded down in order to install it, but then there's a gap between the 2nd row captains chairs and the area that the cargo screen is supposed to cover. Not the best design, but if you keep your valuables closer to the tailgate, the screen should do it's job of keeping them out of the view of anyone on the outside.
I hope this helps.