ooh i work freelance for Barney's. I just shoot the windows every three weeks but I do know a bit about it. Barney's does tend to have smaller sizes and the look for mens suits has been very tight fitting skinny legged pants, which Morrissey only wore briefly in the early 2000s or so (short, narrow flood pants have been the in thing for top designer suits lately) - but Barneys does Made to Measure suits and I am sure they can work with Morrissey.
In general its a younger, hip, rich crowd and sorry to disappoint you america haters - not all americans are fat, esp not the rich ones.... its the poor who are generally fat. Barneys keeps clothes for customers they market to... I am sure they can accommodate Morrissey - in fact stylewise he is so Barneys... at least in my view. He could be the poster boy! Old world elegance meets sleek styled luxury.