Welcome to BYC!
I don't think there actually is a place to buy broody hens anywhere! Hens can't be really be controlled to go broody unless you inject them with hormones but that would be very evil and wrong! A hen will only go broody if she's ready and if you were to transport her to a new location she would most probably stop being broody! Your best hope would be to find someone that is selling their hen which is broody at the moment! And most likely if you take her home to your place she'd stop being broody! Some broody hens will even stop being broody if you just pick them up and move them around in your yard so I doubt that a hen would stay broody if she were moved to a new home!