You may be able to access temporary, small amounts of power via:
Portable power banks or chargers
Portable chargers are small, reusable batteries that are designed to taken with you anywhere and used to charge small devices like mobile phones and tablets. Portable chargers are helpful tools, however, it is important to remember that they must be charger prior to use. You can purchase these chargers from almost all retail stores that sell electronics.
Solar mobile phone chargers
Solar mobile phone chargers are available at most camping/outdoor adventure and electronics shops. Typically, they need access to full sunlight in order to charge and provide power.
Car chargers
Most modern cars have USB outlets (or similar) that can be used to charge small devices. If a car does not have this feature, it may have a cigarette lighter socket. A cigarette lighter adapter with a USB port can be plugged into the socket to access small amounts of power. Adapters can be purchased at almost any retail store that sells electronics.
Wind-up chargers
Wind-up chargers can be used to top up a small electronic device’s power. The operator simply needs to wind the handle provided to generate small amounts of power. These chargers will work in any conditions; however, the power they provide is minimal. Specialist electronic retailers often sell wind-up chargers, as well as some camping shops.