Since I’m in the Missouri Ozarks, I buy my seeds from https://www.rareseeds.com/ aka Baker Creek Seeds who are also in the Missouri Ozarks because I figure, after several generations, they’re acclimated to the basic same climate and soil conditions that I have.
High Mowing Seeds is supposed to be a good one and they’re in Vermont so that might be a good outlet for you New Englanders.
I just received my Baker Creek catalogue. Their organic seeds are very good. In fact we are eating New Year’s collards from the garden today I raised from Baker Creek seeds.
Baker Creek actually only grows some of their own seeds. They contract out the rest, because in order to maintain isolation distances they would need a farm bigger than the entire state!
(I’m one of their growers, and I’m in Wisconsin.)