Look for a reputable breeder on the AKC website. Please be cautious and buy only from a reputable breeder who is breeding for the betterment of the breed and not to make a buck. Back yard breeders are not only irresponsible but you could end up with a dog that has health issues throughout it's life.
Have you checked PetFinder or your local shelter. I can promise you you will find a perfectly good dobie in need of a home. You'll pay less money for it and you'll be giving a homeless animal a home. Buying from a breeder only supports the pet overpopulation.