This seems to be a good reason to carry one of the jumper battery
systems.  I carry, bungeed behind the passenger seat pedestel, one of
the 17AH jumper batteries.  So far, in this Westy, I've never needed
it for myself but have used it several times to help others.  It also
has a built in air compressor for tires or other inflatables and I use
it for other 12v applications away from the Westy when camping.  When
camped for extended periods (like a week at a time), it doesn't get
used for anything, it's my 'just in case' starting battery.  Also much
easier to attach to another vehicle than jumper cables from your rig.