http://www.klassewoodsnaturalfarm.com/index.php
They have both pasture-raised chickens and eggs (along with turkeys & beef). I've been ordering chickens from them for years - they are incomparable in taste.
I'm not sure you'll be able to find just chicken breasts though from anyone who raises their chickens that way. Usually they will sell you a whole bird. It takes a lot of chickens to fill up a Costco-sized tray of chicken breasts, and most small-scale producers are not willing to do that.