I bought the Duckworks system (link below). Even though it's black it doesn't heat well enough in the northeast, so we heat water on the stove and blend it as needed -- then carry the full sprayer into the head. It works quite well for our vacations and overnights, and is sparing with water. We use it when we're anchored for more than 2 days. If we were live-aboard I'd like something like what Max did.

The Duckworks system is $38 (about $50 delivered)and yes you could piece it together for maybe a few dollars less but you'd waste a lot of time and maybe it wouldn't save at all when you add up costs of the pieces and individual shipping. They're certainly not getting rich off it.