You could look for some breeders or aviaries in your area. Maybe Google on one of those terms and the name of the species of bird you want. Most areas have bird clubs, too. They usually know who's breeding particular species. If all else fails, try posting an ad in the pet section of Craigslist, saying you would like to buy some birds. You might get a breeder to respond or just someone that would like to re-home some pet birds.