Actually I do have electrical tape on some things, but some of them are really hard to wrap effectively with enough tape to obscure everything, and plastic covers are easier to pull off when I really do need to see the lights or lcd display or whatever.

you trying to sleep on the bridge of the Enterprise or what? hahaha!

all joking aside. even with a 3d scanner, you will be hard pressed to create a model that exactly matches the dimensions of something in reality. and 3d scanners, especially cheap ones, are VERY noisy.. meaning the resulting model it creates will be a mess of random blobs of false hits all over your model that you have to clean up.

the better option might be to measure the device, and create a custom cover for the part. i imagine its something like stereo or DVD players or something right? if you want a flip up cover, you might create hinges that can double sided tape to the top of the device and allow a flap to come down over the display, perhaps with some soft weather strip along the edges on the back to make a better light seal.

but, failing that, and the electrical tape. i have one more idea. powerstrip/surge protector! just plug your devices you want dark into them, then flick the switch off at night before bed! hehehe, couldn't resist

Thats all it takes to make a faceplate/enclosure for something with perfectly placed holes.