What kind of vacuums/timers? Coleman? I've always used Dixmor timers with a clear Lexan to protect it, no clear window in the decal, just cut out. Damage due to punching has been a non-issue. If yours are Coleman you may have to have something custom-cut to size and drill holes for it to mount between the bracket and the
door inside. I've ordered stuff from tapplastics.com, just be sure to call in your order. The online ordering doesn't work well and your order will likely be wrong. Once you have something to protect the timer, just cut out the clear window and be done with it.
FWIW, I've also had lots of trouble lately with people filling the reject chute with pennies, nickels and dimes. My first thought was to use an extension behind the cup and cut them so it will still catch quarters, but smaller
coins will fall through on the ground. There used to be a
coin acceptor that had a catcher made of wire that did the same thing. Then I saw the extensions are like $16 each, so I'm thinking instead I'll just remove the cups altogether and let idiots pick up their change off the ground.