Suit slacks

The difference in size between jacket & waist is called the "drop".  Standard drop is 6-8 inches, depending on manufacturer, which is why you're seeing 40-42 pants.  It works out for most people (i.e. I'm a 38 jacket, 32 pants.) Going down an inch or two is no problem, six is impossible without ruining the drape of the pants.

you have 2 options: 1) Find a store that will let you 'mix and match' a suit jacket from 1 suit and the matching trousers from another. Most will not, but some do. Depends on what range in price we're talking. I guess you could also get away with taking a few suits in the dressing room and trying to pull off a switch... this is easy if you're talking Dillards, Hechts, etc., not so easy at a high end store 2) Have the trousers re-cut. Not many places do it but some do, and in your case for just about every designer it would be a necessity. It's just like it sounds... they literally re-cut the trousers. You'll have to call around to the high end men's stores and tailors to find someone who will do it, and it will cost a bit, but if you're making a big investment like most do when they buy a suit, it's obviously worth it. 2-3 inches is the absolute max to have trousers taken in without throwing off the balance. Hope this helps