I built my own wash down kit. The backplate on your brakes have some rubber stoppers in them. If you pull one of those out, you can push a nylon hose fitting in there.

Go to Home Depot and buy 4 plastic hose fittings, a couple Ts, a few hose clamps, a female fitting for your garden hose, and enough hose to connect all the pieces. For about $20 you can build your own.