Hello George,
Welkom!
Is this a project for a museum? I'm not sure if toys would apply as museum quality replicas and they are rarely in scale to each other. 1:10 scale is also rather uncommon for big prehistoric mammals. BUT for a museum quality project, you may want to contact sculptors/artists, for example from this forum, and commission someone (or more people, if you need a lot of these models) to sculpt such models for you.
I would also like to invite you to have a look at our website Likaon Wildlife Models. We are a team of sculptors. We have 3 Ice Age mammals sculpted by Jose Miguel Aparicio, for example. These models are in smaller scale, not 1:10 but 1:20. They are down the page.
[You must be registered and logged in to see this link.]You can also check this page, Eofauna produce high-quality replicas, but the scale of this one is even smaller - 1/48:
[You must be registered and logged in to see this link.] I also recommend this website, shows beautiful work of master Feng Shan Lu, Mountain Animal Studio:
[You must be registered and logged in to see this link.] I'm not sure in what scale his prehistoric mammals are, I have some of the models of extant animals and they are in 1:15 if I remember right.
By the way, do you want to include any models prehistoric horses in this project?
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Anna
Horse and Bird studio - Horse sculptures
My model horse collection