There aren't specialty shops where you are? I wear a 12, and usually avoid the issue by wearing loafers or fairly unisex lace-up shoes bought in the men's department for work. However, when we lived in eastern Kentucky (not very progressive, to put it mildly, quite rural, and filled with people rather shorter than average Americans), lots of people told my wife where we could find shoes in large sizes. "Go to this store in this town. (It's where the drag queens shop!) They have shoes that will fit." They carried up to size 15 in stock, in all kinds of styles. I'm not sure why everyone invariably told her that it was where the drag queens bought their shoes, unless they were trying to hint about our relationship, but it was definitely where tall women shopped. Nobody else carried anything bigger than a 10, and most places didn't carry 10s.
I haven't looked around St Louis, where we are now, personally, but a quick search shows several stores in the area that carry at least some women's shoes in sizes through 14 or 15.