Hi digga64,
Welsome to Rootschat and the Emigrants to NZ Board.
There is a branch of the New Zealand Society of Genealogists (NZSG) at Te Awamutu, a bit north of Otorohanga. It might be worth contacting them at TeAwamutu {--at--} genealogy dot org dot nz to see if they can assist. I suspect that they may charge for any research, of course.
Once you get back to the next generation it should be possible to find a record of their naturalisation (National Library here in Wellington hold a useful index of naturalisations to 1948).
Let us know how you get on. Any questions, just ask.
Regards, riley
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