Just keep your eye open. You might consider an Abetta saddle. They come in 17" seat sizes and their regular tree fits a wide variety of horses. They do have a "wide" tree as well. Abetta's basic "All Around" square skirt saddle in a 17" seat is $345 new from this web site: Abetta Cordura All-Around Saddle
I have an Abetta endurance saddle and it lasted many years of hard riding. It's still usable, just not as pretty as it was new, lol.