Thanks for the vote of confidence Vintagegamer but that is a type of glass that I don't do.
However, If you can remove the back glass that is still there you should be able to go to any good glass/door/screen shop and get a piece cut to size. Explain to them that it is for a vending machine. They should tell you to get a tempered glass. Have them bevel the edges so they aren't sharp. it will be a few extra bucks but worth it.
Or I might be able to take the whole machine off your hands.