If an animal shelter or rescue doesn't meet your needs when you're looking for a specific type of puppy, you're going to have to do some research into the breeders and even some pet stores in your area. However, when buying a puppy you need to understand that not all breeders are created equal, and neither are all stores.
When it comes to breeders, they run the gambit. There are the hard-core, dedicated breeders who have a single purpose in life and that is to better the breed of the dogs they are dedicated to. Then there are the hobby breeders. Those who take great care of their dogs and breed great pets, but not necessarily champions for the show circuit.
In the breeding world, the only breeders you need to run away from are the puppy mill breeders. These are the scum of the scum, the low of the low. These breeders could care less about the dogs they breed and only care about profit. They are known to produce puppies with health issues and emotional impairments. Never, under any circumstances, buy a puppy from a puppy mill.
And that brings us to the pet stores. Pet stores have gotten a bad rap over the years because many of them get their puppies from puppy mills. There are, however, exceptions.
If you have a small locally-owned pet store in your area, they may buy their puppies from local hobby breeders. Some even provide free vet care, health guarantees, etc. If this is the case, buying from them is not the cardinal sin of buying a puppy. That being said, it will be expensive. These stores have to make a profit. They pay a quality breeder, and you pay a markup on top of that.