Due to current regulations it is illegal to sell e-liquids that contain nicotine. 

You can import nicotine for personal use the links below are the ones that I have used in the past and have found to be reputable, it is also advisable to use DHL shipping where possible. 

When ordering nicotine base to add to your e-liquids make sure you order 100mg PG based

 Always store your nicotine base in the freezer (it won't freeze) and always shake well before use. 

You can get your nicotine from 1 of 2 places:

Freebase nicotine:

https://www.mixologyvape.co.nz

Salt nicotine:

https://www.mixologyvape.co.nz

If you use the code "vapersedge" at check out it will give you 20% off

https://liquidnicotinewholesalers.com

These guys have both freebase and salt nicotine 

If you use the code "vapersedge" at check out it will give you 15% off