I have designed this pocket light around some scrap parts: a primary Li-SOCl2 cell sized 14500, a white LED, a slider switch, a locking push button, and a few resistors and transistors. The circuit in the schematic is a simple constant current source and the resistors are chosen such that the current can be set to about 10, 3, or 1mA; which, considering the infrequent use, will make the light run forever. ** A FreeCAD design file is published here: https://odysee.com/@ZigaMDIY:9/PocketLight6-FreeCAD-file-ZigaM20220212:6 Tips and support kindly accepted here: https://paypal.me/ZigaM3 Or with LBRY (LBC) credits, through my Odysee channel: https://odysee.com/@ZigaMDIY:9 I also design on redbubble: https://www.redbubble.com/people/reintegration/shop And I promote my RB designs on Pinterest: https://www.pinterest.com/reIntegration42