There are a number of Canning Stock route songs I've come across including the Slim Dusty song, but of course they're not the one I'm looking for.
Ted Egan wrote Bringing the Beer to Broome? S'truth! Good on ya mate! After singing that song for 20+ years I finally know who wrote it, not surprised its Ted Egan.
Maybe I should just be bold and try emailing some folk clubs and singers down under. An old friend of mine has been living there since the early 80s and hits all the folk festivals he can.