Bead Blaster

Anybody in the "We Cheap Club" know of anything to use for a lens protector
in a glass bead cabinet besides those $3 a piece plastic ones you can't see
through after a half hour? There's gotta be something out there, I just
can't think of what it would be. BTW, built my own 4' long cabinet, got
about $300 in the whole thing, works just as good as my little brother's
$1200 one except I can get a motorcycle frame in mine.
  Jim K.