Based on the PiJuice HAT released in 2016, the PiJuice Zero allows the Raspberry Pi Zero to be used on the go away from a power outlet. Pi Supply has developed a software suite to help get you started and has included a low-profile to keep the overall build size small. The PiJuice Zero is available to order on Crowd Supply now for US$45 with orders shipping worldwide on October 31.
https://www.notebookcheck.net/PiJuice-Zero-An-Uninterruptible-Power-Supply-UPS-for-the-Raspberry-Pi-Zero-that-costs-US-45.426833.0.html