OP - I don't fully understand your options. Do you have a floor drain and hot/cold water supply somewhere? If you so might be able to rig something ...
http://shop.sportsmansguide.com/net/...FcQc6wod738AWQ

http://www.ourcampsite.com/shower.html

http://www.campist.com/archives/gran...ging-room.html

http://adventure.howstuffworks.com/o...g-showers1.htm

http://www.bajataco.com/shower.html

http://forums.mtbr.com/passion/campi...er-541838.html