If you're looking for a specific type (as opposed to generic chickens), you might try eBay, or maybe better, EggBay. I sometimes cruise eBay at least to see what people are offering, and you can sometimes buy small quantities of eggs from private individuals (between 4 and a dozen), and then hatching them out in an incubator would be in order.
Hm....EggBay seems to be temporarily disabled, I know not why or for how long. Many interesting links from this site--
http://www.geocities.com/KelliAnn293/great_links.htm
You also might see if there are any local petting zoos that have chicks or chickens for sale. The local one around here offers their surplus chicks for sale every spring (Silkies mostly here) Also farm papers often carry ads in spring for people selling chicks locally. I also cruise the Sunday papers want ads for what kind of livestock is for sale (or I used to anyway).
If you are not particular about the kind of chicken (I am not fond of Leghorns or the production varieties that go by numbers. I prefer some of the strains with established dispositions.), you can also try feed/farm stores in spring. They often order up chicks for local people and will sell them out in smaller lots some times.
It's a long story about myself and birds. Had them my whole life, everything from Budgies to ducks, geese (or goose, a Toulouse I saved from the dinner table), pheasants, pigeons and on to raising Budgies, Cockatiels, & Bourke's Parakeets before I developed hypersensitivity pneumonitis and landed in the hospital on oxygen because of my severe allergy to birds (from long exposure). I am hereditarily one of the 5-15% of the population susceptible it turns out.
So no more birds for me. 
Now I'm trying to content myself with the guinea pigs, dogs, horses, and turtle that I've rescued. I still come on the bird boards to answer questions from my long history of misadventures in bird keeping in case it will prevent anyone else from having a tragedy.