You can't buy them in the US. You could buy one in Mexico and drive it across the border, but you wouldn't be able to register it in the US. It is probably possible to legally import one but it would be very expensive and time-consuming, and you'd need to know a lot about import law.
AFAIK if its registered in Mexico it can be driven in US under temporary import permit. I've seen the odd Hilux or other new rarity that way. Quite common to see Mexico plates here in AZ in all number of cars not available for sale.