Want to go really cheap?

If you have or can get an old water house cut off a foot or two of the end that you screw a nozzle on or fits into the city water input on your camper. Then buy an air male chuck and a screw on ring O clamp and clamp the air chuck to the piece of water hose. Crank your air compressor regulator down to 35 to 40 psi, connect your piece of water hose to the city water port and then open up the valve on the sink  and you'll be as good as gold! Make sure before hand you have by passed the hot water heater, took out its anode rode and drained it (leave the anode rod out until spring when you de-winterize) then go through the camper one by one opening all valves and don't forget the toilet valve (the flush). It's so easy and only takes all of a half hour to 45 minutes to winterize. Then all you need is a splash of RV antifreeze in the drains and toilet. The only down side is you have to have an air-compressor but it gives you a great excuse to buy a new tool if you don't have one!