I had great success in a similar situation with a flexigullet saddle, but honestly if I'd had the option I also would have preferred a changeable gullet.
Wintec saddles with adjustable gullet. I love mine and can swap out the gullet to don't nearly any horse thick or thin.
Wow saddles are adjustable, they can be adjusted to fit any horse, they were adjusted to fit a
Long horn bull once, they will fit anything!!