Yes, New Zealanders 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 while away from home, there is a 3 day waiting period (72 hours) from the time you buy the policy until cover starts. There’s cover during this waiting period for an acute serious illness or an acute serious injury as a result of an accident. All other cover begins after 3 days/72 hours or on the commencement date of the policy, whatever is latest.
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.