U CRAFT 'EM!!! seriously. That's how you get 'em

To craft one, you must kill a wild one and the one you kill there will be a Blueprint for it in its body. The blueprint level is determined by the wild level you killed.

They have shield that block damage by hit counts, so its best to use a fast firing dino(velonsasaur) or auto weapon to destory one, they drop blueprint of themself

You can also craft a level one in any terminal around the city if you want one quickly

Each on I kill only seems to be worse than the one you craft at a terminal, even the max lvl ones. Official settings.