I seem to be having trouble getting a reasonable quote for travel
insurance that is longer than 30 days.
I was going to go to Oz for a couple of months, but can't find any
insurance.

What country are you in ?

I see that you have discovered one of the little quirks in the
"vacation" industry. 30 day maximum coverage for most travel plans is
fairly standard as they are designed for travel on vacation.

Here, I can buy travel medical for trips up to 183 days. Some can get
coverage for 210 days.