There are Scimitar-horned Oryx and Addax on game ranches in Texas. They obvious do well in that State, so they could always simply be released into the wild there. They'd be far safer there than in their former habitats (the Oryx mentioned is extinct in the wild).
I'm not thrilled by the idea of hunting such a rare animal, but those ranches took something like fifty of the species back in the 70s and now number around two thousand. So despite culling the herd every year (and having hunters pay a great deal of money for the chance) they've actually done quite a bit to save the species.