I feel your pain, but not personally (I wear a size 6). However, my husband is tall (6’4") and wears a size 14 to 15 (depending on the type of shoe). He cannot get tall boots in his size unless he goes custom. The ONLY boot that he can get in his size is a Justin Roper (which is a paddock boot—he just removes the little fringe “garnish” that makes it look western). They come in sizes up to 14, I think. And he has custom half chaps for his super long, thin, calves. Recently he checked into custom boots and is still waiting to hear back from the tack store to see if the manufacturer is even willing to make him custom boots.
I feel so bad for him because I have all kinds of “off the shelf” options ----I have summer show boots, paddock boots, winter boots, boots for traipsing through a muddy pasture, etc. ALL of them are readily available, and most were on sale. He has NO options for winter boots. I even tried to find the boot cozies (not sure what they are called)— the neoprene covers that go over the toe of your boot to protect it and keep your feet warmer. But again, they didn’t come in a big enough size. So I do understand how limited things are!