As far as I have heard Standard Rex are not all that easy to find in the US, it's the Mini Rex that are popular over there. I would try contacting ARBA and asking if they could recommend a breeder. Hopefully someone who can be of more help will be along soon. Good luck in your search.
I would suggest contacting a breeder even if they are not Rex breeders becasue they may know someone who does breed rex. If you are not looking to breed rabbits you may look into some shelters.