There is, and I have one. I will have to look back to see where I got it—but I can tell you for sure it was something I learned about on this board. It is a small piece of plastic with a fresnel lens that just sticks to the inside of the windshield and lets you see the traffic lights without bending your neck down. Of course I can honestly say that I still often bend my neck down because the fresnel lens makes things smaller and it is still easier, if more painful, to just bend my head down!
was it sized for the top of the windshield?
barring something fitted for this purpose, you probably could cut down something like this for vans into a narrower piece.
of course, install it upside down so it's viewing up vs. down