I can't speak to local sources in NH, but there is a website I've used called The Flour Sack that sells Sir Galahad and other King Arthur flours in various sizes from 5 lbs to 25 lbs and it tends to be less expensive than buying those little bags directly from King Arthur.
Try your local bakery, they may have it. If they do not, they maybe willing to order you a bag on their next delivery.
The name of your town is certainly appropriate for a baker!
You could try calling one of these foodservice distributors to see if they carry the flour and if they will sell to you.
Associated Buyers, Barrington, NH, 603-664-2424
Favorite Foods, Somersworth, NH, 603-692-4990
I can't speak to local sources in NH, but there is a website I've used called The Flour Sack that sells Sir Galahad and other King Arthur flours in various sizes from 5 lbs to 25 lbs and it tends to be less expensive than buying those little bags directly from King Arthur.