Hello! I'm in Barnstead, 30 minutes from you!
I use Chichester Blue Seal, on Rte 28 for cornish x's. They run about 1.65 a piece. Their number is 603-435-6942. If you call, they can give you a schedule of when they will be ordering chicks through out the summer/fall. I found it was a lot cheaper for me to order from them, per bird, then to use most online sites.
There is a person in Barrington right now, though that's a ways away from you, maybe 45 minutes, that is selling 3 week old Cornish for 3.00 a piece... I know that doesn't help you out this fall..but anyone else local that is looking to grab them now... the ads been on craigslist nh the last couple of day.
Tractor Supply Company on Rte 4 (Chichester too, I think) right before Concord , often has chickens available in their store. Their number is 603-798-4424. They also have a flyer there that lists all the poultry they sell, and their prices, and you can order almost any time I think, and pick up at the store, though I might be wrong..they may have set days throughout the month. I think they are a bit on the expensive side, but they have a great variety of breeds, incase you are looking for something other than cornish X.
You will need to purchase your dual purpose birds asap if you are looking to slaughter this fall, but if you want cornish, like another poster said, they are usually butchered by 8 weeks, so you could purchase in August/September and butcher in October.
Good luck!
-Jessa