Some smaller/moderate size US breeders (who have websites or are on Facebook) that come to mind for having really nice quality (movement and brains) youngsters are:
Timbach Farm, KC Dunn (Indiana, near KY border)
Rolling Stone Farm, Mo Swanson (PA)
Maplewood Farm, Jen Vanover (NY)
Windy Ridge Farm, Judy Reggio (PA)
Majestic Gaits, Kathy Hickerson (NH)
Windmill Farms, Jennifer Zauel (IL)
Imajica, Liz and Madeleine Austin (VT)
Lio Lomas, Deborah Harrison (CA)
Shooting Star Farm, Scot Tolman (NH)
Now this list is mostly Dutch…since that is the breed I am most familiar with…but I am sure other people can chime in with more breeder names/other breeds. The amazing thing about networking with a breeder, is they will help you connect to other breeders. When I went to look at a weanling last year, the breeder showed me all of her weanlings/yearlings…then took me to another local breeder to see his young stock, AND placed a call to another breeder to see what she had available. Even though that meant risking I wouldn’t buy from her…she was happy to support any of the breeders in her network. (In the end, I bought one of her yearlings! And I absolutely love him!).
Here is the KWPN-NA Breeder’s Directory…https://kwpn-na.org/breeding/kwpn-na-breeders-directory/ I am sure other breed organizations have similar information on their sites.