I first ran into this idea in a hotel room. They had a motion detection light under the bed which would turn on when you got up in the middle of the night. It only lit up the floor so as not to disturb your partner. I tried to replicate it with a common battery operated LED motion detection light. These two pieces work with a Mr. Beams MB722 stick anywhere light.

I printed these out with 30% infill. Strength isn't really an issue. You may not need the top shade if you have it far enough under your bed so that the bed acts as the top shield.