- For larger stationary instalations any kind of 12v battery with USB car power should work. Add a solar panel for perpetual power. https://www.voltaicsystems.com/blog/powering-a-raspberry-pi-from-solar-power/ has some good info on this.
- https://www.adafruit.com/product/1566 (15 hours)
- https://www.voltaicsystems.com/v44
- https://uk.pi-supply.com/products/pijuice-standard seems pretty cool if you want something compact and feature rich.