Jerommel
(Jerommel)
5
You can find 2 different sheets of diffuser film in LCD monitors.
So if you find a broken monitor somewhere, you can take it apart and source 2 sheets.
One is some 5° and the other some 20°, maybe more than 20° (my guesstimates)
You can cut discs and glue it on the glass lens with Kafuter UV curing glue or what ever you prefer.
Glueing eliminates the mirror effect between sheet and lens = less loss.