I've been looking around for a Flash backglass lateley, but for a bit more money got myself a used Galaxy backglass with a whole machine attached.
I'm getting fussier with machines myself as i go. Gave the Flash playfield/plastices etc. a good clean polish and wax, the thing now sparkles and plays excellent. I also straightened out the coin door (it now opens and closes perfect), and gave it a polish. It's like a different machine.