Heritage birds, so called, are breeder blood lines that fanciers and loyalists to the breed have kept for decades, in some cases 100 years. This is what makes them so special and only really available through careful breeders of the breed in question. Some show their birds, other breed/raise them for 4H kids and others in the fancy, while others simply love raising the birds, enjoying them as chickens and breeding them faithfully, year after year.
We've got a Heritage thread for almost every breed here on BYC. There you can find discussions, eye popping photos and interesting people. Many good breeders and devotees of the breed hang out there and contact can be established.
Hatcheries serve an entirely different purpose. They are mass producing birds, for the most part. They are a business and must be profitable to stay in business. They are to chickens what McDonald's is to food. Is McDonald's food clean, fast, and cheap? Yup. Is it the same as a gourmet restaurant or a home cooked meal by grandma? No way.
With a hatchery you'll get an available, mail order, healthy bird for the most part. That's the good news. Will be even close to the standard for the breed? Heaven's no. That's not what hatcheries do. Hope that is said in a fair and honest way.