I think my TB has finally passed the point of no return and needs to go up a tree size Mr Princess&thePea would probably love a "floofier", more modern saddle, but for now, my wallet and my short legs are demanding that we stick with our Kieffer Wien and its 15.5" flaps.
Tony Webster in VA can do it. Virginia Saddlery, I think? Just make sure whomever you use IS authorized by Kieffer. Many of them will adjust the saddle, but if they are not TRULY authorized by Kieffer, it will void the warranty.
"If you don't know where you're going, you'll end up somewhere else."
I used Dressage Extensions. Trumbull Mtn has a great how-to for taking tracings, so I used their instructions, took pictures of the chalk marks on my horse, and sent everything to DE. I still paid a saddle fitter to come out and adjunct the flocking.
A helmet saved my life.
2015 goal: learn to ride like TheHorseProblem, er, a barn rat!
If your saddle is under warranty, you'll want to go with a fitter who's "approved" (for want of a better word) to do that work, or you can void the warranty. However, if the saddle's second hand and there's no warranty issue, Patty Barnett in CT does that sort of work, and does it well. All she'll need is a tracing of your horse's back taken 3 fingers' width behind the scapulae.