Trade Me is probably cheapest if you're getting one or just a couple. But more than that have a look at https://ru.nkon.nl I've ordered a few times from there and haven't had any problems.

You can get an entire dyson handle with cells already done on aliexpress when I was looking for other accessories.

Just be careful - many cheap 18650's out there are either a low capacity or are at risk of catching fire.

Make sure you understand the safety of LiPo batteries and understand just what you're buying. Stick to trusted brands (Samsung or LG) and if your appliance is high drain ensure that the 18650 is rated for a high drain appliance. That being said, many laptop batteries are just packed full of 18650's and many people have used those to repack other batteries.

I have a draw full of 14.8v 4C batteries if those are of any use to you? I know they're not 18650's but if you have a project in mind then you can have them for the cost of postage.

blakamin: Vape shops.

For a premium! 

TM seems to be good for no name batteries (and the rather ominously named "UltraFire").

I need six for the Dyson. It'd be good to find a reputable brand, Panasonic etc, for a decent - less than $10 each - price.

My brother in AU used to work at a medical tech place and their buy price for Panasonics was apparently around $1 each - but they would have been buying them in Tesla quantities. I don't mind paying a few times over for scale, but $30-$40 each seems excessive.

I read (possibly on GZ) that the cheap 18650 cells are recycled from laptops. You probably want branded, guaranteed new.

I considered those cells for a torch, but shopping around I just bought a couple of torchs that works well with AAs.

Trademe ones tend to be parallel imported alongside other china import stuff. And the rest of the world all but refuses to ship them to NZ unless you go via europe postal companies (or they smuggle in devices like gutted TV remotes like I found recently...)

Jaycar use to have pure Panasonics, but you pay a penny for them when you want to make a pack of 4 up for bike lights. But bound to last longer than the 3 import packs I've had (including repurposed laptop cells)

https://www.jaycar.co.nz/18650-rechargeable-li-ion-battery-2600mah-3-7v/p/SB2308 

Oblivian:

 

..And the rest of the world all but refuses to ship them to NZ unless you go via europe postal companies (or they smuggle in devices like gutted TV remotes like I found recently...)

 

 

 

If buying from overseas sellers, you run the very real risk of never getting them. They can get confiscated at Ch customs
Ive had several batt orders never actually make it out of China . Reputable asian online sellers now wont even sell batts to NZ .

Torch Monster perhaps?

https://www.torchmonster.co.nz/accessories.html 

pbolger:

 

TM seems to be good for no name batteries (and the rather ominously named "UltraFire").

 

I need six for the Dyson. It'd be good to find a reputable brand, Panasonic etc, for a decent - less than $10 each - price.

 

My brother in AU used to work at a medical tech place and their buy price for Panasonics was apparently around $1 each - but they would have been buying them in Tesla quantities. I don't mind paying a few times over for scale, but $30-$40 each seems excessive.

 

There are LG and Panasonic 18650 cells on Trade Me. Did you look at ru.nkon.nl, 6 samsung cells would be $30 shipped.

I dont trust the "genuine" 18650's off trademe, if you want something decent and don't mind paying slightly more for peace of mind, buy them from PB.. $20 for 2 samsung 18650's use promo code WHOLOVESPB for free shipping

EDIT: also 2x LG 18650's for $20 bus less mAh 

These are free shipping to NZ. High capacity quality Samsung batteries. 

https://www.fasttech.com/product/2363300