The Harbor freight sprayer mentioned above might be just as good .. not sure. It's worth going to look at the quality of the construction.
The fine spray of a garden sprayer is too much of a mist to be good as a portable shower or something for washing gear.
So I went to Home Depot and bought the hand sprayer and hose that connects to a kitchen sink for washing dishes. That sprayer has a spray switch built into the handle. It was under $10 for the hose and sprayer together.
http://www.homedepot.com/p/DANCO-Fau...-202305850-_-N
I then went to the brass fittings dept and bought a straight in-line connector that presses into the garden sprayer outlet hose that I cut off near the tank, and screws onto the bottom of the hose for the dish rinser.
I fortified the connection of my dish rinser hose to the tube coming up from the garden sprayer tank with a split piece of auto engine hose (3/8", I think), then covered that with a fat piece of electrical shrink wrap that fits over a battery cable. It made a very clean transition from the garden sprayer tube to the sink hose spray nozzle. This prevents kinking the smaller diameter garden sprayer tube at that point.