I think Wargames Foundry models are metals, but Aztecs nonetheless …

Aztecs

There are some in 1/72 (you can find almost anything in plastic in the 1/72 scale by model companies, they are cheaper on average then the other scales, and there is a big hobbyist run review site, so you might want to make that your go to war gaming scale).

However there are  none in 28mm-32mm plastic unless you count GW lizard men,  just like there is nothing in plastic 28mm for Imperial to present China (not one dynasty, not even warring states or three kingdoms, not even fantasy), Egypt (you would think it would have something, but no),   or any of the other slash and stab era none Western cultures outside of those that fought western powers in overly dramatic battles or wars that everyone knows about and got blockbuster movie treatments like the Persians (300 Spartans vs. thousands of Persians) or where too significant to Roman, Medieval European,  and English/British history to not mention (Crusades without Muslims makes no sense, Mongolians finally got sets, some North Africans are a must in plastic for Rome except Egyptians cause Cleopatra didn’t do enough apparently,  and you can’t play Sudan or the AWI or the Zulu conflict without some natives).

Meanwhile we have not 1, not 2, but 3 different  manufacturers covering Vikings and Saxons in plastic (2 will be covering Normans in the near future), same deal for the Napoleonic war’s western theater, more Greeks sets than I want to think about let alone buy, close to all the medieval era troops of Europe, close to all the history of Rome is covered, not even going to talk about WW2, and practically every era of British soldier except WW1 or those  conflicts in Asia and the Pacific outside of WW2 from what I can tell.

The notable exception to this trend has been the Sengaku era Samurai sets that are produced by WGF and are now distributed by Warlord’s. I think it has to do with current rulesets and to a lesser degree pop culture more then anything else, so the Aztecs may see plastic in the future.

Actually the Ghost Archipelago tribal set is more like a mix of Polynesians cultures with a dash of Inca thrown in, and armed with hybridized North east cost Amerindian weapons and a pair of South African shields. I think it would be smarter to  just go with metal (unless you want to proxy lizardmen for humans).

Eureka miniatures have a range of 28mm Aztecs in metal