In the absence of more interesting things here’s a quicky before I go and cook tea.. I have a Lezyne Femto Drive front light for my bike, tiny thing with 15 lumens of output – useful for a bit of extra visibility in crappy weather or in winter for when your ride accidentally extends into dusk. Useful to take touring. Now that long winter nights have arrived it also makes a handy little tent lantern with the addition of a diffuser made from an old 35mm plastic film can… I guess not everyone still has those eh? But I’m sure you’ll find something similar. In this case the internal diameter of the lid from a Fuji film can is a really good friction fit over the light. Cheap and light (ahem).
Lezyne claim 30hrs from 2x CR2032 button cells, which are really cheap. The sort of thing Poundland sell by the bucket load (well, 6) for, errrm, a pound. Just remember to recycle the cells rather than sling in the garbage when they’re done.