After doing some more research, it appears the only manufacturer that makes boots in a Mondo 32 (the direct equivalent of a US 14) is Scarpa. The two online retailers I found that sell Scarpa AT boots in these large sizes are OMCgear and Bent Gate Mountaineering; though, the Canadian company Mountain Equipment Co-op is also selling them in these sizes.
Update
I bought the stiffer version of the Maestrale (white), and I have had a terrible time with pain in my feet from them. I've had the boxed out once as they do indeed run narrow (may do it again), but it seems to be do to my arch support once they're buckled down now. If I were buying again, I think I would go with the cheaper less rigid orange version.