Resist the temptation to rush. A good dog is worth some patience and research. Almost every breed club has a handful of dedicated people who locate, rescue, care for, and then adopt out individual dogs of their chosen breed. We have used these groups for both locating and placing animals and have been very happy with the results. Contact the club and ask them who does their rescue work.
Every area has a shelter that houses lost, abandoned, and stray dogs.
These hardworking places can be wonderful sources. Many animals end up there because their owners were less than ideal, not because the dogs were. Talk to the kennel people, ask them what dogs might work for you. Go back a few times. If you are serious, a shelter is usually happy to help.