OK, so to add and trying to be clear for the jetlagged in the room 😉
You can’t buy insurance somewhere you are not resident (from what I’ve checked in the past)
First one from google
https://www.rentalcarprotection.com.au
Hire a lot over here at the moment, basically you put your card down against the damage excess – that is the max you are liable for – normally about £1000 these days. If you don’t take insurance form them in the event of a problem that can go from your card or not be released.
If you have 3rd party insurance any claim is down to the rules they stipulate (there is still an excess generally on those policies too). You claim through them to recover the loss.
I’ve seen some of the global ones being a little better if it’s non fault and the other party has admitted liability – ie somebody runs into the back of you – you can pass over details and get that taken care of by the insurance only.
For a single trip take a look at what they charge – for less hassle it’s sometimes just worth knocking it down to a sensible excess with the company – I have an annual policy so don’t.
Make sure you have your passport with you, and any other ID docs you have.