If you're feeling homebrewish you can make your own
using a laser printer to print the gratings on overhead
projection foils.
You'll have to come up with the artwork yourself
(unless somebody hacks it up and posts it).
Note that it has to be designed for the refractive
index and thickness of the plate stack.
The rest of the parts are a bunch of plexiglass
(or glass) sheets, one frosted, something to
wrap around the whole unit once completed, and
a mounting bracket.
