We've been looking at reducing water use this spring; someone else might find these products useful:
OAS(1) showers cap water at 5-10L per use, no matter how long you shower. Getting this installed also means we can swap our water heater to run on the solar array entirely, since you're not flushing all that energy down the drain while you shower.
Waterless urinals(2) use no water at all. They work by keeping a layer of oil in the trap instead. Pee sinks under the oil layer and out of the trap, oil stays in the trap since it floats on top. So, stays just as clean as a regular toilet, with no water hookup.
Disclosure: None, I've got nothing to do with these companies, other than buying their products for my cabin.