“Just get hold of a LiPo battery and plug it in. It gives out 1A which is great for powering a Pi Zero (though not a Pi 3 which has higher power requirements). It has a charging circuit built in which saves you getting a LiPo charger.”
“It's small, and it can power your Pi while it charges your battery and it switches seamlessly between battery power and USB, what's not to like?
Works a treat!”