You could also use "Poste Restante" an international postal convention, ... mail marked "poste restante" would be held at the post office for at least 2 weeks ...
Plan on say 3 to 7 days from Sydney to Darwin delivery and say 1 week from there - that would give you a lea way of a week.
Simply have the parcel addressed to
"me - first name, LAST NAME"
--- That should get it to the central post office in Darwin. And you won't be tied to any hotel/backpackers etc.
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S