I used to get them at these places: kroger grocery store, gordons food service (a food wholesaler that has a grocery section open to the public) martin's grocery store (this place had seeds twice as strong as anywhere else), rural king, and an amish store that I forget the name right now, but it is way out in the middle of nowhere.
It has been at least 5 years, probably more, since any of these places had good seeds. They changed somehow. But I checked one place and they worked again. I am not sure I want to go check around town for seeds, as I don't plan on getting addicted yet again. But, I have a feeling that however they changed the seeds, it cost them money, and as soon as the 'publicity' about the seeds faded, they went back to the cheaper ones that we like.