Several parrots and related species that are capable of talking can be found on the Birds Now website. This website has ads from private owners and aviaries. Many of these birds are young and have not been trained to talk but are of species that are most able to learn.
The only sure way to get a talking bird is to hear it talk in-person before purchase. Many species, including pet parakeets, can learn to talk if given enough attention, time and are talked to regularly. Some species, such as the African gray parrot, pick up words and other sounds easier than others.