For our nightlight I used one of these:
https://www.superbrightleds.com/moreinfo/led-wired-bolts/little-dot-smd-led-accent-light/639/Mounted inside the existing bathroom light fixture, spliced into power there and drilled a hole for a small switch on the side. Just one is plenty bright, takes next to no power, they run off of 12v and have an adhesive backing. Available in red too if that's your fancy.
If you really want to be slick replace the fixture's switch with a double position one so one way is night light, other regular light, center off.