There were probably fifty vendors displaying sunglasses this year at the show. My final choice was the Lo-Pro from Numa Sport Optics. Their wrap-around style provides excellent UV protection from snow-reflected sun, and their slightly curved temples with a grippy rubber surface allow them to be stowed on the brim of Bob's cap when not used and still hug his head well enough to stay on should he become startled by wildlife.
But what really sets the Lo-Pro sun-glasses apart from all the other brands I saw was their extremely flexible frame material. The material makes them virtually unbreakable - an especially important consideration in Bob's case. You can see in the second picture just what you can do with one of the Numa frames - a different one from the first frame. Plus, should Bob still manage to destroy them somehow, Numa provides a low-cost, lifetime replacement guarantee.
Available since Summer, 2007.