The company Thompson and Morgan sell them but I don't know if they deliver to NZ. Perhaps check on their website.
I know NZ is very strict with their bio-sanitary laws so they may not deliver there.

Yes, Seaburn, they are strict. When we arrived in NZ in November, anyone who came in with hiking boots had to hand them to be thoroughly washed.

NZ gardeners cannot buy from T&M but there is a website which does sell bulbs within NZ. www.nzbulbs.co.nz can be contacted by email to find out if it is possible to source tree lily bulbs. Lots of their bulbs may not be available at this time of year. The tree lily is a specially bred Oriental lily selected for its 6-8ft. high stems which can have up to 30 blooms per stem.

Thanks for info tried nz bulbs and waiting for reply but looks like not available here