Yes, Australians can buy a World Nomads policy when already overseas!
You can most definitely buy a policy even if you’re already travelling, working, living or studying in another country.
If you buy a policy when you're overseas and the policy start date is within 72 hours of issue of your Certificate of Insurance, you'll need to wait 72 hours for cover to begin. However, if you suffer a sudden illness or serious injury as the result of an accident after the state date, there's cover for emergency overseas medical expenses and emergency transport expenses straight away.
If you purchase a policy when you're overseas and the policy start date is 72 hours or more after issue your Certificate of Insurance, cover for Cancellation or Trip Interruption expenses will begin 72 hours from the time we issue the policy, with all other benefits commencing on your departure date
You can also keep buying more cover while away from home to extend your trip up to 12 months in total by signing into your World Nomads membership as long as you extend it before the policy end date (before midnight Australian Eastern time) and the same product is available.