Hi Mike. I am not too up to date on bow making but a person who may be able to help is Toa Hunter Gatherer. He lives in the Waikato and has a Facebook Page and Youtube Channel.
He has a business making his own bows. I don't know if he is a good contact but he may be worth a shot.
You may have seen him on Maori TV, he has an outdoors/adventure show there which he hosts.