For my Sony laptop I got a piece of 1/8" red acetate and a piece of
1/8" gray. Together they allowed too much light through. I went back
to Tap and picked up a small sheet of the darkest window tinting film
they had and stuck it to one side of the red acetate. Works great!
It took a while to work out the bubbles in the film. Maybe you could
have them put the film on for you. I'm sure there is a trick to it that
I missed.
By chance the acetate sheet was just a hair too small in height. I
found that I can tape it over the display with the gap at the bottom.
It keeps me from getting "flashed" when I walk by the laptop and helps
illuminate the keyboard.
Hope this helps.
--Gary