I bought some clear acetate sheet in 1985 to place under the glass on my bead blaster cabinet. I figured to replace it fairly often. It is still there!
I didn't attach the sheet to the glass, I just placed it over the opening, then laid the glass on it, and clamped it all down. There is foam weatherstrip between the cabinet and the window assembly.
I think the acetate has enough "give" that a glancing blow from the bead doesn't leave a mark.
The only people that use the cabinet know to not let the bead hit the window. In a commercial environment, this is impossible.