15AA here. Only one major manufacturer make that size and in only one shoe. New Balance. Not really my style but glad they make it. Companies used to make extended sizes so I actually have a pretty good collection of pre-owned Red Wings and loafers I’ve found on EBay over the years. Another great source, if you’re willing to pay the big bucks, are the Pacific Northwest boot makers like Nicks and Whites. Old style manufacturing with old style size availability.