Only from a nursery/garden centre in New Zealand, Joybelle. You won't be allowed to import this South American plant.

Why not Bulba? Is it NZ regulations, or UK too? Is it invasive/ a problem? Please elaborate. (quick google shed no light)

Any plant/seed sent to New Zealand needs a licence. Depending on variety, some are more restricted than others.
Sweet peas are commonly sent to New Zealand by major seed suppliers here to grow over there, then the seeds are exported back for sale...all to do with seasons.
Same with dahlia tubers. They can be exported with lots of certificates guaranteeing cleanliness, virus free, etc.

NZ regs Kere no non-native plants may be imported.

NZ is probably one of the most strickt countries for the import of seeds and other plant materials - local regulations. Whilst i doubt that vetches are dangerously invasive they do seed around a lot and NZ is becoming very precious about its native flora and fauna.