And don't forget that in inclement weather, that a solar shower can be filled with water heated on a stove or in an electric kettle.

Another alternative Is a large drum filled with warm water. Use a 12 volt submersible pump, a length of garden hose and a hand held shower spray.
The water in the large drum may be heated on a camp stove or in any other way. Two kettles of boiling water, diluted with cold water should be enough.
The 12 volt pump can be worked from a vehicle battery.

This can be used indoors in a bathtub, or in the garden if not overlooked, or in a tent in the garden.

Water in dark coloured garden hose soon gets hot in sunny weather. Not much good for showering as it may be too hot, and soon becomes cold as the water is replaced with cold water.
Can be used to fill the drum as described above.