There is a ready supply of bicycles with dynamos around here. If you lift the back wheel off the ground and pedal hard you can get at least some energy. The old

There is a ready supply of bicycles with dynamos around here. If you lift the back wheel off the ground and pedal hard you can get at least some energy. The old ones are very basic too. With more time and need one can probably rig a small stream to do it instead.