I'm no expert, but have some familiarity with U.S. insurance.
In the states, you can get homeowners/renters insurance, which will cover stolen goods, including bicycles and other personal property. Since you are neither a U.S. homeowner nor renter, I doubt that you could buy this kind of coverage. Same thing with liability coverage: it is usually included with a homeowners/renters policy, with the option of adding more coverage under what is called an 'umbrella'.
I will echo staehpj1, that you should shop at home, starting with whomever is your local insurance agent.
Hopefully, a fellow Aussie will chime in with some good suggestions.
As a side note, I have never had a loss while touring, in either the U.S. or Europe, and doubt that you would need this kind of coverage.
On the other hand, medical coverage is a MUST. Make sure your medical costs are, at least, partly insured.
Hopefully, another world traveler will chime in on this important topic.