if one has a flat tire, one fixes the flat tire. no need to go to a store or find replacements. you always bring a tire repair kit, spare inner tubes, a pump, and you fix it. if you can't do that yourself, you have no business touring.

people have toured around the world in one set of tires. shredding a tire outright, provided the tire is of high quality and designed for the rigors of touring, is rare. but if you still want to be safe, just carry a spare foldable tire. I am on my second tour with Schwalbe Marathon Supremes 42-406, and they are still like new. I have had no flat tires since i installed them in October 2016. Schwalbe Marathon Supreme or Marathon Mondials is what you want. Regrettably they are no longer made in 406 size. you can still find discontinued Supremes on the web, but they ain't cheap. if you decide to go with ISO559 (26") tires, the Surly Extraterrestrials are also worth a look.