Solar showers work very well and they are easy to roll up and stash, weigh
nothing empty and are cheap.  We've been camping with them for months at a
time each winter in Baja and in the desert southwest.  They last about two
month before springing a leak somewhere.  Yah, you have to have some sun and
yah, sometimes the shower is not super hot.  But then they don't have any
moving parts nor do they use fuel or make noise.
  At times in the desert they get too hot and you have to add cold water to
be able to stand under it.  That luggage compartment on a Westy would be a
perfect place to set one out for sun.  Some type of a hoist or a hook is
needed to elevate the bag enough to get comfortably under it during your
wash..  In a pinch, if it is cloudy for too long, you can heat water on your
stove and fill the sunshower for a quick rinse.
  We never go long without taking ours along..
  Don Hanson