so what would be a good place to shop for this kind of thing?
There's a mall by me which has a Nordstrom and a Bloomingdales, both of which locations are blessed with Tailors and staff who more or less know what they're talking about. Macy's would be a couple steps below, and in my experience their staff is capable of getting something out of the back... and not much more.
Once you know better what you're looking for, then you can pick specialty stores. For example: You might find a
(Hugo Boss) suit that you like a lot... so you check their store.
{edit} - You might also look for a haberdasher in your area. They're in the business of making you look good. Though that can come at a little cost sometimes.