Of course Rancourt is no G&G but I was able to do that with a pair of cordovan loafers I ordered via their custom tool on their website. I found that when I ordered a pair of loafers from Brooks Bros that going down a half worked for the small foot but just too tight on the larger foot. Going with my normal size and I was unable to keep the shoe on the smaller foot. With the custom order via the Rancourt site the problem was solved with one foot using the normal size and the other a half size down.
There are a few brands that will do that including AE.