I bought one of the Speira Mammoths. It's very nice, good size to scale and IIRC a decent price. I left it on my tabletop one night and when I came to it in the morning the Alliance and Linear A Amazons had got to it and made it their pet.
Monmouth the Amazon War Mammoth
To be honest he seems to be quite happy about the arrangement.
I also have another one somewhere from Mixvs Minimax (this post - here
viewtopic.php?f=11&t=17329&p=190718&hilit=mammoth+mammoth#p190718), I don't know if he is still selling his range of figures which includes other paleobeasts as well. He is very nice too. I wanted him for a Skyrim game but he keeps going missing and I haven't worked on him.
Crom's Anvil do a range of critters, terror birds and the like - in 15mm - but they could be useful. They are sold by CP Models
https://cpmodels.co.uk/?fbclid=IwAR0vad ... 0grBX8wCHgHope this helps.