retail, need 1 or 2 batteries, can be from reclaimed laptop batteries etc
Plenty on TradeMe. Probably cheaper options from overseas retailers too.
Or you mean retail as in a physical store? Jaycar have them.
You can't buy 18650 batteries from any of the overseas sellers now. All the Chinese webshops stopped shipping to NZ because of the lithium battery restrictions on aircraft (Which ironically also includes NiMh batteries) and Aliexpress sellers only accept DHL/Fedex, which makes it completely unaffordable. Anything declared as "battery" are being routinely intercepted and rejected by the postal services.
Your only real choices are Trademe, Jaycar or Mr Positive.