I stopped at Cabela's in Rapid City, SD, Scarborough, ME, Sidney, NE and Reno, NV. They had defensive ammo available but I haven't had a problem getting that stuff mail order from them with fairly short wait times so I didn't buy any as I have a pretty good supply on hand.
I was more interested in plinking ammo. I managed to pick up a little over a 1000 rounds in .380, 9 mm and .45 from the various Walmarts that I stopped at. I'll have to take another trip when I use this up.
I did think about Kittery Trading Post and was going to stop there on the way out of Maine but for some reason I forgot. I have shopped there in the past.