Yeah, Axolotols are the only exotic reptile or amphibian you can own. Another example of an animal being rare in the wild but common in captivity you could have could be the crested gecko (If they are legal). They were once thought to be extinct but rediscovered, and are now one of the most common reptiles kept in places where they are legal, they are beaten only by the leopard gecko.
Sadly, crested geckoes are not legal. I wish I could display New Caledonian geckoes but it doesn't seem likely to say the least. Here's a list of the lizards that can be kept privately in NZ (other than natives which can be kept with a license) and a list of ones that can be imported for MPI-approved zoos.
Private (rough order of rarity):
Blue-tongued skink.
Inland/coastal bearded dragon.
Eastern water dragon.
Leopard gecko.
Cunningham's skink (very rare but bred in rather small numbers).
Shingleback skinks are kept privately however they are old and dying out and it is unclear whether they were actually imported legally.
Importable for zoos:
Green iguana.
Fijian crested iguana.
Lace monitor.
Komodo dragos.
Shingleback skink.
Madagascar giant day gecko.
Scheltopusik.
Frilled lizard.
Veiled chameleon.
Present in zoos but not officially importable:
Jackson's chameleon.
All of the privately owned species apart from bearded dragons.
There's a lot of turtles present legally in NZ private ownership but only the following (that I know of off the bat) have significant breeding populations:
Red-eared slider.
Snake-necked turtle.
Reeves turtle.
Australian painted turtle.
Carolina box turtle.
Hermann's tortoise.
Greek spur-thighed tortoise.
Crocodilians (saltwater crocodile and American alligator) can be imported only for zoos. Snakes are not allowed under any circumstances, even zoos and laboratories, which I suspect is more about keeping our positive image as a snake-free country more than for actual biosecurity risk.