Boondockers -- Why take up space in your camper with a permanent shower stall that you use once a day! Watch to learn how singer-songwriter Laurie Jude Theodorou has used a few parts from Home Depot to make an easily removable RV shower stall.
Besides the shower curtain, the key ingredient to this system is a water heater drain pan that you can buy for $12-15 and stow away when you’re not using it. The optional battery powered spray gun she uses is no longer available, but there are others available.
Of course to make this system work, you don’t necessarily need the water heater drain pan. Any shallow tub that’s wide enough to stand in would do the trick.
As for the hot water — the best tip I take from her video is that heating "shower water” doesn’t need to be any more complicated than boiling 1/2 cup of water on the stove and adding it to your container of cold shower water to warm it up.
For a "shower" — How about the Simple Shower...? It's a specially-made shower head that screws onto the end of not only any 1-Liter or 2-Liter bottle, but also to a Platypus-style flexible drinking bottle.
The price for the simple shower is about $12 plus shipping. It’s still only available at a few retailers, so the most convenient way to get is to Buy the Simple Shower on Amazon