In Los Angeles, the King's Roost in Silverlake resells Central Milling flour that they buy in bulk. I am not affiliated with that business. Just a sometimes customer.
Fellow Arizonan here. 🏜️ The Costco on Sossaman just north of the 60 often has it. I saw it there a couple of weeks ago. You could also look at some of the other locations.... The Costco down near the S Loop 202 and Williams Field exit is bigger and often has more selection.