I have a couple of thoughts regarding suits for a person who wants to add a single suit to his wardrobe. First, can you describe the suit you currently own a bit more? Brooks Brothers have changed over the years in some aspects of its styling. You state that your suit is a classic BB. Is your suit cut in a trad fashion, rather like a sack suit? Does it feature natural shoulders on an undarted jacket with medium lapels and a hook vent at the back? Are the trousers plain-front or pleated, and if pleated, are they forward-pleated in the English style or reverse-pleated? Do the trousers have turn-ups or cuffs, and if so, are they 1" or 1.5" in cuff width? Are the trouser legs baggy, medium, or tight? These details might help us understand the style of your current suit.
Assuming your suit is in a trad style, would you prefer to have another in the same style? And if you do, then I would suggest J Press
in New Haven, Conn., and Cambridge, Mass., as your best option. Their ready-made models start in the $900-$1100 range, and go upwards, although they have a current sale with many suits going for $777. They also have a custom option, which might be the best for you since you have some problems with finding an easy fit for ready-made suits. Their custom suits start at the $1200 price point. You may want to give them a call and ask about the details, and see how well they can fit a man of your proportions. J Press makes suits that are classic and well-made. They have not changed the trad cut of their suits or sportcoats in seventy years.
A second place to shop for classic or trad style suits would be O'Connell's
in Buffalo, NY. They have suits in the $600 - $900 price range, probably some more expensive ones as well. They offer custom trousers, although I did not see a custom suit option when I gave their website a quick glance. Here is their website:
There are less expensive options, like Lands' End YearRounders, or Joseph Bank, but the cut is going to be more contemporary and less classic. Personally, I would never buy one of the modern suits that seem to be all the rage nowadays: Very tight and short jacket with narrow lapels, a very low-waisted pair of trousers, also with narrow legs (in the drainpipe fashion that used to be a craze in the 1960s). I often see folks on TV in these suits with an isoceles triangle of white shirt front showing between the quarters of the jacket and the waistband of the trousers, and with the end of their necktie bisecting this triangle. In my humble opinion, it does not look good -- and that's putting it mildly. I hope I have not offended readers who are enamoured of this style. But if you like classic/trad suits, I would be surprised if you were an aficionado of said style!
Good luck, bonne chance
, bien suerte