I have been looking to buy car hire excess insurance for my rentals here in Australia (just occasional use - like GoGet/Hertz etc) - but can't seem to find it. I wanted to buy an annual policy so as to avoid the crazy per day insurance the car rental companies charge ($15 a day for example).
Using a link from an OzBargain wiki I tried to get a policy through - https://www.questor-insurance.co.uk/vehicle-hire-excess-insu… - but they didn't offer it to Australia. But as an example in the UK you can get an annual policy for around $80.
Goget has an excess cover option for like a few extra dollars per trip.