More suggestions and sources
Burnley, I. H. From southern Europe to New Zealand: Greeks and Italians in New Zealand. Sydney: University of New South Wales Press, 1972.
Fragiadakis, Georgios. The Greeks in New Zealand. Wellington: Greek Orthodox Community, 1990. (This work is mainly in Greek, but there is some English text.)
Verivaki, Maria, and John Petris. Stories of Greek journeys. Wellington: Petone Settlers’ Museum, 1991.