Any source that is local is the best. I get mine from a company in Essex,Ontario and i'm not sure if they will ship to your door in New Zealand. Get a small test bag and try to sprout it. If it doesn't grow in 18hrs then it might not be the right kind. I can send you the address if you want to ask them but I don't have that off the top of my head will have to look it up. I will post here with that info.
www.topcrop.ca for Millet that malts.
www.topcrop.ca for Millet that malts.