Your vet will not usually find this. All reputable breeders sell pet quality puppies with spay or neuter contracts. Such a clause shows the breeder will always be interested in the welfare of the puppy - for its entire life. Observe the adult dogs in the house. Be sure because this is what your puppy will mature to look and act like.
All puppies are cute and lovable, but they grow up to be like their parents.
Only buy from the actual breeder of the puppies. Brokers or middlemen are only interested in making money. They are not interested in the welfare of the puppies or the breed. It is uncommon for reputable breeders to make money. They breed for the love of their breed and their dogs.