There appear to be 41 immigrants to New Zealand based on the New Zealand Naturalisataion records, 1843-1981 with the last name Hanson prior to World War II. There are about 396 with the surname of Hansen with an "e" on those same records.
This may not entirely answer your question as these 41 became naturalised citizens and would not account for those who may have entered NZ but met with disease or death or took a return trip home....
