I would say a work around for those shops, that are difficult, might be to take in wheels without the vehicle and just order tires and have them mounted.Tire shops are getting finicky about mounting anything other than exact factory size so it's almost hard to go with a taller tire if you wanted to. I personally love the like of a big wheel but hate the risk associated. I'll take a 70/17-18 any day of the week.
Then install wheels/tires at your house.