I have a few Pi Zero W boxes that I run on batteries to take on the train with me. What I've ended up doing is adding an LED power indication light, and a button to press to power it down. You have to do a little soldering, unless you get the headers you can hammer in, but you still need to connect wires to the button and LED. I'm not great at soldering, but I've managed to pull itby 3pk - Raspberry Pi(rate)Box