I have an old slide viewing system^1 Simon SVS 5822 which rear projects
an image to a screen which is damaged.

The screen's material is clear lucite with a front film for image
diffusion.  That screen diffusion film was damaged by some kind of
chemical reaction with its included shroud type plastic cover during a
long time in unused storage.

I'm trying to replace the approximately 8" x 8" (20x20 cm) screen with
something which will function similarly for viewing, and I haven't had
any luck so far with the local camera store, glass store, or plastic
materials shop.

If I can find satisfactory material for the rear projection diffusion,
it needs to be cut precisely to fit into the viewing system.  Or maybe
there is such a thing as a film which could be applied to clear glass or
plastic.  So far I haven't found a frosted glass which would work;  it
seems that obscuring glass these days is coarsely rough instead of
finely granular.

^1 If you want to get a view of what I'm talking about, here's some
pictures from one advertised for sale on ebay
http://cgi.ebay.com/SIMON-SVS-5822-SLIDE-VIEWING-SYSTEM-SLIDE-VIEWER-NICE_W0QQit
emZ270219887176QQihZ017QQcategoryZ83877QQssPageNameZWDVWQQrdZ1QQcmdZViewItem#eba
yphotohosting
or shortened link  http://snipurl.com/22aqy