Getting stuck outdoors without clean water is not ideal. The GRAYL GeoPress Water Purifier Bottle lets you turn any dirty water safe and clean to drink. It removes viruses, bacteria, and protozoa in addition to dangerous chemicals and heavy metals. It can purify 21oz of water.
The GRAYL GeoPress bottle has a replaceable purifier cartridge that is good for 65 gallons. It gets the job done in 8 seconds. You can find out more about it here.