Mm.
Okay , there are lots of different possibilities for the energy source. We could use a basic battery , but that brings with it , like they need to be recharged and the bulk , the size of it as well. And they're not so great to dispose of , environmentally.  There's a hand-powered dynamo which is a sort of thing that was used for torches fifty years ago. A bit out of date. Kinetic energy is something that's been recently developed.
Um  What is a hand-powered dynamo ?
Um , where you manually charge up the power.