Restaurant Depot in Minneapolis will carry All Trumps. It's wholesale, but with a few loopholes. If you know someone with a business/tax id, that's the best option. Some Restaurant Depots are known to give out one day passes to the public. I get the feeling that it all boils down to who's working the front desk. Instead of saying "I don't own a business, but I'd like to buy some stuff," I'd say something along the lines of "I'm in the process of getting my catering license and would like to buy a few things." It's worth trying. Not only will they have All Trumps, but it will be the best price in the area.
Some Costcos carry All Trumps. If you have a membership, I'd give them a call.
Sam's Club has a house brand Bakers & Chefs High Gluten Flour. It doesn't have the protein of All Trumps, but if that's your only option, it's better than King Arthur.
If you google wholesale grocer minneapolis, it will give you a map with locations. Click on 'more results' and start calling everyone on the list. Ask them if they sell to the public, and, if so, do they carry high gluten flour.
Lastly, there's always a chance a local bakery will order an extra bag of flour for you. They might mark it up a bit, but it will probably be less than having flour shipped.