It's packed away right now, but I made a version of this one minus the bowl for a basin. Two buckets, a one way pump (I used a fish tank siphon bulb), some tubing, and a spout of your choice, and you've got a handwashing station. Get a piece of wood and something to make a simple bracket from if you want to secure the bulb to a base instead of letting it hang out in the dirt.
Camp Sink - Temporary Hand Washing Station: 8 Steps (with Pictures)