Looking for a decent (Hugo Boss level) blazer, I think blue, to wear to causal events with dark jeans and loafers

I'm 50, 200 pounds 6'1" . Not out of shape but slim fit doesn't work

https://bonobos.com/products/unconstructed-italian-wool-blazer?color=navy&irclickid=R%3A%3A3ll1kDxyPRQSTliwT41pmUkFULPStRx6oQg0&utm_medium=Affiliate&utm_source=Impact&utm_campaign=Impact_Prospecting_94385-768773&Cvosrc=Affiliate.Impact.Impact_Prospecting_&Affiliate_id=94385&click_id=R%3A%3A3ll1kDxyPRQSTliwT41pmUkFULPStRx6oQg0&irgwc=1

Check out this from Bonobos

Or this from Suit Supply https://suitsupply.com/en-us/men/jackets/navy-havana-blazer/C6765.html?utm_campaign=237913&utm_source=AwinUS&utm_medium=affiliate&awc=16225_1694818865_cc7b2b578cc383e76be02e6aca31181f

This is the kind of thing you'll rarely get lucky with ordering online. Even the same size from the same brand will fit differently.

So I need to head to Nordstroms I guess

Department stores, Brooks Brothers or other mall specialty stores, and there's also the ever-ubiquitous Men's  Wearhouse/Jos A. Banks.

You might be surprised, though, at what you can get custom for the price points you will see at some of these places. How far are you from New York City?

About 2 hours from NYC and 1.5 from Boston

Nautica

The one I linked is Nautica but any off the rack brand like Ralph Lauren or Calvin Klein works great.  If you have Hugo Boss or the like money, then even better.  Given my uses I don't want to spend that much on something that might risk being damaged on a call or rumpled sitting in court etc.  

Sometimes I prefer to order and have it custom tailored.  I am a big buy but not a blob.  Alterations are cheap and take it that one step further.  Search for "cobalt blue".  It's not as dark as traditional navy and not as bright as a royal blue.  I wear suits in plain clothes LE but also have to go to some semi formal cocktail parties and such with my wife for her work.  A blazer in that color with a good quality button down, super dark denim and a pair of clean polished cognac/whiskey tan leather shoes and matching belt is a showstopper.

This might help a little

As others have said, you’ll need to go in and try them on. Most manufacturers have different fits. I have had decent luck with suit supply for the options and money.  They’re used to tailoring around a gun

Do yourself a favor, should you strike out with local stores (though I suspect you'll find something if you just put yourself out there. It's kinda like women). Too many men hate to shop, and finding the right clothes sometimes takes looking in enough stores to stumble across the perfect one.

However... there's a thread in this forum about Proper Cloth T-shirts. They also make excellent suits and sport coats, custom made for you, and at prices comparable to some of the stuff you'll se in stores. But... you'll definitely want to get down to NYC, see/feel the fabrics for yourself, and get measured.

Suit Supply