Don't overlook "Sunshower" or "Sun Shower".  I used to see these in the catalogs and think they were the ultimate in silly gear gimmickry.  Then a friend of mine brought one on a climbing trip....  You'll be suprised at how well these work.  They're cheap, portable, require no intallation, etc.  Obviously they don't get as hot or heat on demand like the other complex systems, but for $20 or less you can't go wrong.  I keep one in the camper at all times.  Packs small and is light weight.  Throw that thing on the luggage rack for a few hours and you'll be pleasently suprised at the results.
Mike
Here's one source
http://www.campmor.com/webapp/wcs/stores/servlet/CategoryDisplay?categoryId=14962492&storeId=226&catalogId=40000000226