I would go try on 2 last models in those sizes if you can. My standard advice would be to try an 11E, since an 11E is shorter and wider than an 11.5D. Even if its a big snug, it could certainly be stretched another width or easily to the width of your current shoe. You might try a 10.5EE also. For example, I measure an 11E, but the best fit for me in the 5 last was a 10.5EEE.