During my years working in plain clothes I always had new trousers modified for carrying my sidearm. The material taken off when the trouser legs are hemmed can be saved and used to make belt loops that will accept the belt to be used, and those loops can be sewn on in places that will not interfere with holster placement.
Many suit trousers and slacks have belt loops that won't accept belts wider than about 1.25". I prefer a 1.5" heavy-duty belt to support my holstered weapon.
I also had sport coats and suit coats modified with a layer of light canvas stitched into the lining around the waist and hip areas. This helps to prevent "printing", and also doesn't get torn up by the rear sights, hammer, etc, like the typical jacket linings will do.
A couple of heavy fender washers stitched into the lower hem of the jackets at the front will keep the jacket hanging straight and neat, avoid exposing the holstered weapon inadvertently, and aid in keeping the jacket out of the way when you push the jacket back to reach for the weapon.
Since all of my suits, sport coats, and trousers were so modified for my work as a cop, everything became a tax-deductible expense.
Best regards.