If you prefer a specific breed, such as Persian, then search for the appropriate breed rescue society. They can put you in contact with foster carers who are seeking homes for cats of that breed. Keep an eye on the local rescues and shelters, and ask to be on a notification list if the type of kitten you seek becomes available. Be very careful about sourcing kittens from the Internet, as they may not have been raised humanely and be part of the puppy (or kitten) mill trade!