Found! Travel insurance for 90 year old!
With overseas travel now getting much cheaper, here's some extra good news. My friend and I are travelling to the UK for 23 days in May. My friend is a very healthy 90 year old, but was prepared to submit a current medical. She found that the only company that was prepared to offer online insurance was Medicare Private (she is not a member, members get a 10% discount). The cost was $478 for the 23 days. The excess for medical treatments under this policy is $5000. To cast aside all doubt she phoned Medicare Travel Insurance before sending off the form and was assured, that as any medical treatments she's had were more than 5 years ago, that she could go ahead and apply and pay online! She decided that the opportunity to travel, for the sake of insurance at $21 a day, was well worth it. The UK has reciprocal health care arrangements with Australia, so don't forget to carry your Medicare card.
I am aged 63 and used Columbus Direct which I've found to be the cheapest for my age group. The cost for 23 days is $104. However, as I am a frequent traveller I chose their Worldwide, annual cover (excludes USA, Canada,China and Japan) at a cost of $250. The excess for medical treatment is $250.