It would have to be something you do custom.
Protecting only the glass seems to be most peoples concern, and is doable. When you are trying to protect the body work too, it becomes a bigger project. That is my interest.
So far, I've always been able to stay out of hail larger than pea sized, but I know my day is coming. If you get close (I do), you eventually will get bit.
The idea I'm working on will give me a rectangle on the roof of my Xterra (mounted to its factory roof rack). Each side, the front, and the back will have panels that "unfold" to hang out over the sides of the truck and over the windshield and rear glass to provide a metal umbrella. The frame and unfolding panels will have expanded metal or expanded aluminum sheets covering them that can be replaced if badly dented. To protect the hood and front fenders, I'm considering doing what Tim Samaris (sp?) did to his white truck, and have a panel that mounted to my bull bar that covers the front of the truck (laying just above the hood). In Texas, you are allowed to hang up to 3" past the fender line on the sides. The Xterra has really big fender flares, which will really help me....
This kind of material and fabrication doesn't come cheap. Even staying as light as possible, it will add a lot of weight to the top of my Xterra. It will make noise. It certainly won't help gas milage. It'll have problems. It'll be a PITA. So, I continue to draw up revisions to my plans and think about it.....