I was trawling for an airfare (MEL-LHR return) for a 4 month holiday and one site offered me travel insurance as an add on to the airfare for a mere A$67!
It looked fairly good conditions too (seems to have no excess which I find hard to believe):
The site was https://au.gotogate.com/
I'd got myself an ANZ Premium credit card which has insurance and costs A$87 per year, but this seems better. Long list of excluded sports including zorbing and hydrozorbing!!