When I go to the US I get a dealer demo bike on an extended basis, or one of their trade bikes not sure how insurance works coming the other way but my travel insurance covers me for any vehicle I ride / drive when I travel internationally. I would email some of the dealers around Melbourne and see what they say?
What is the name of your travel insurance you use internationally.
I bought vehicles in the US quite a few years ago (near 30!), and if the seller left "the tags" and the number plate on the vehicle then I could drive it prior to export out of the US.