It will be difficult to find someting OTR. I am 6'0" 158 lbs,, have narrow shoulders. I am a 39, but usually go with 38 suits because of the shoulder thing. It's hard to find 38 suits, much less 36. I was in Neiman-Marcus - Chicago a few of weeks ago, they had a floor full of suits, not a single 38. The salesman told me to go to the NM in San Francisco, they have more small-sized suits there.
Wow, what a helpful suggestion by him ! It would have been a much shorter hop to New York and you can bet they would have the stuff there, and if not in NM, some other stores.