Or just a bowl of hot water and a towel. Takes up less space and can be used for multiple things. I personally don't like the 'just a shower' concept. seems a bit excessive to bring along something that does just one thing.
For a while I had the Coleman instant hot water heater, which also had a shower head and a pump, so you could use it for a couple things. Plus it had overheat shutoff. It worked pretty well.
But in the end it took up space and weight and was one more thing. We already have something to heat water in (pot) and on (stove). Throw in a rag and clean yourself up. Or just hang out with people with showers.
Simplify.