Sidi Dominator 5, Sidi Bullet II, Sidi Blaze. In these models, Sidi makes up to at least a Euro size 50 which is just about a US size 15. You may also be able to find the "Mega" version which is for wider feet.

Head over to http://www.sidiusa.com/ and click on US Sidi Dealers to find a local shop where you can go and try on a few shoes. I also wear a US size 15 and must say the best way to get a good fit is to try them on locally.