So Medium to High cost. Buy water from somewhere like meco, bring propane and buy one of these. https://www.amazon.com/Eccotemp-L5-Portable-Tankless-Outdoor/dp/B000TXOJQ4/ref=sr_1_1?ie=UTF8&qid=1493616693&sr=8-1&keywords=propane+shower

Shower over a grey water collection.

Or I guess get a ridiculous bus RV with an indoor shower. That's probably the actual high cost.