On this Mr. Prepper guide page, you will find information on how to get a Miner Helmet.
The flashlight in the helmet doesn't run out of energy – creating one helmet will allow you to use it for the rest of the game, even in dark rooms or at night.
You need Miner Helmet to explore the mines in Mr. Prepper. The only way to get it is to craft it after unlocking level 2 Workbench. At an early stage of the game, you can have problems with obtaining electronics - check the "Plastic, electronics – where to get?" section of this guide or dismantle a device from the house to obtain it.
The Miner Helmet is illegal! Take it off and place it in the inventory before an inspection.