Hi
You could try the online Cemetery records - in the Resources section on this board. They don't cover every cemetery in the country, nor do some of the sites, include cremation records.
So you definitely know that he has died in New Zealand but do you not know where he lived ? Or even have an idea of when he might have passed away ?
Sorry, not able to help much.
If you have access to the NZ BDM Indexes on microfilm, (the death records go up to 1990), then that would be the other thing to try.
Lu