I made a holder for my car type Satelite Navigation screen to fit onto my motorcycle. These are not as robust as the motorcycle versions so need protection. I hand carved a cradle out of expanded polystyrene into which the items fits quite snuglyand this gives it all the protection it needs.
So get yourself self some expanded Polystyrene and make a holder for your glass. It will survive anything almost that you care to throw at it.
Place some thin closed cell foam padding between the glass and the holder once fitted; it will afford some shock protection. I would be surprised if anything breaks as I sometimes walk with others here using a 4x5 kit and never broken anything. You'd have to be pretty rough with the pack: falling, jumping, crashing, banging against trees, rocks etc., to bring about damage. A camera falling off a tripod head (I have seen it happen...) is an entirely different matter.
I've used polycarbonate, acrylic, and hobby plywood. Velcro buttons can be used to keep the barrier in place, or some camera backs will have
some kind of other feature to keep the protective piece stationary. I wanted to do something a little cooler looking for my 8x10, so took some
copper-clad PC board - thin, strong, and very stiff - and did a swirly true verdi gris color treatment on it. Guess I "spit-toned" it!