Lumintop Pico / Olight I1R EOS - both about $15 - 20, shorter than an AA battery, 100+ lumens for 1/2 hour. Built-in USB recharger.
When you’re done playing with it, hook it on your jacket’s zipper pull and always have a flashlight.

Wurkkos WK30 Lightbringer suggests is a great choice, White, Red, UV!

or go for another multi-emitter, like the Sofirn C8F (21700) or Lumintop FW3A.

So many ways to go - wall of light, thrower, something with Aux lights, super small,