Hi Cosmickiwi.
I lived in NZ for 9 years from 2008 till 2017 and the main reason I left was actually custom issues. I did manage to import some plants and compounds but I did fall under controlled delivery and my address was flagged by customs after the second delivery... I would be careful with phalaris, I heard from people here in Europe that toxic compounds require a lot of work to be excluded.
Mushrooms and Salvia Divinorum are easy to obtain within NZ - I grew salvia at home without any issue, actually with perfect weather conditions it was the most successful harvest I've ever had.
I recall the episode of a guy who imported large amounts of mimosa and found police waiting for him at home - I would suggest to try with small amounts via the Netherlands suppliers or Australia - I did receive several packages from Australia with plant matter without any issue, always small amounts at a time.
Hope this helps - any questions feel free to ask.