Red Light Torch
This basic red light torch should be on every astronomer's keyring. Lightweight, simple to use and, importantly, red!
No fussing with different modes, just press the button and a red light appears. Sufficient to read and illuminate a little distance around you. Even if you have a"proper" red light torch, it's worth having this tiny gem around.
If you want it on for a while without pressing it, there is a little plastic slider that keeps it On.
Uses a pair of replaceable CR2016 batteries, which are included. It is very fiddly to put the torch back together after unscrewing, so consider it disposible.