(edit - G+ suspended me so I deleted my G+ account)
Amazon.com: Insta-Cling Extra Dark Professional Tint Film: Automotive
This is not a bright idea, but a dim one. My thrive has really bright LEDs and the screen - even at minimum brightness. When I'm doing astronomy I don't want to kill my night vision or even checking a map in my car (parked, of course). I did this with my laptop screen years ago and it works on the thrive even better given the smooth glass screen.
Insta-Cling 5% VLT (visible light transmission) film. You might be able to find 2.5%, but it might not be that clingy plastic. I just cut out a piece to go over the LEDs, then another for the screen (with a cutout for the camera and ambient light sensor) and now it is dim enough to use at night, and it packs small and touch works through it.