1 - Go to local dog shows.
2 - Introduce to yourself to every breeder that is there that day, get their information & give them yours.
3- Research. Go to their websites & VISIT the kennel first hand. You will know right away. If they refuse, walk away & go to the next breeder. If they are not friendly and are desperately trying to make an acquaintance, walk away.
4 - Ask to see the parents. If they are good reputable breeders, they will help you see both parents. 50% of the time the stud may not be from the same kennel but they should be able to locate him for you.
5 - Ask TONS of questions. If they shy away skip around any question you may have, walk away.
If you're looking for a mix, you can easily go to a shelter and find plenty there that need to be saved. If you're looking for a puppy but have zero intentions of a show quality (meaning they still look like 100% pure bred but to the average person would have no clue), just let the breeder know you want pet quality.
Sounds like you want to train it in obedience. I would advise looking into local shows that support Obedience, Rally, and Agility competitions vs Conformation but if it were me I would want to see all the many events & them performing.
If you need a hand in finding a local show near you or how to get going, just drop me a line. Otherwise, there's always tons of local shelters with dogs that need adoption. There's also Australian Shepherd rescues & Border Collie Rescue's and organizations trying to find fosters a home. Of course, they may be older and not a puppy. On the flip side, they may have been already trained, house broken, & ready for their for ever home.