Pocket beagles were bred in the 1300s and 1400s and were said to be about 9" at the withers (shoulder). There is no such thing as a modern-day pocket beagle and in fact, the term "pocket beagle" has become synonymous with poor quality puppies bred for the pet market, and often sold to pet shops. Reputable (U.S.) breeders breed according to the Standard defined by the American Kennel Club and the National Beagle Club of America, which defines one breed with two height varieties: not exceeding 13" at the withers, and not exceeding 15". The light bones, high ear sets, and toyish heads that tend to go along with very small sized beagles are listed as faults and don`t resemble a true Beagle. You will notice the accompanying photo looks nothing like the Beagles shown throughout this site, and other sites of responsible, reputable, preservation Breeders.
In addition to not breeding according to the standard, the majority of "pocket beagle" breeders inbreed to produce the smaller size or have introduced Mini Dachshunds and Chihuahuas to further reduce size. You will see this if you see puppies listed as "pocket beagles" that are merle or blue with blue eyes. This is NOT desirable and frankly, you are paying a premium price for a Mutt. These dogs may be registered with unknown registries. They most likely will not resemble a beagle as adults. In other instances, the term "pocket beagle" is used as a marketing ploy to sell puppies who will end up a normal size at adulthood.
If you still want a small beagle, then consider the option of adopting a fully grown adult from a rescue or the pound. Most beagles are fully grown by about1-1/2 years, and breeders can usually tell by about 8 months if a beagle will remain under 13".