I ride my 19hh, 2100 pound Percheron with a 17", wide, County dressage saddle and it fits him beautfully.
I got the girth thru Dover Saddle, longest dressage girth they had and I am not on the first hole. His bridle and bit I got from Meader Supply (draft horse supply store). I ride him now with a bitless bridle which I got online, draft size and fits him great.
Meader Supply has a great online catalog, and they specialize in draft horse everything!
Drafttack.com. I think that's the site. Good quality stuff and not super expensive. eBay might work, too, just don't buy one of those new tack sets that's uber cheap. They're complete crap. Posted via Mobile Device
The good thing is english and dressage saddles that will fit are fairly easy to find. A good quality MW, W, XW..., or a 33 cm and larger saddle tree will typically fit. I ride in both a 35 (thinner more modern Percheron) and a 37 (mutton withered curvy Percheron mare). The problem is finding a good quality girth to match. I use a 40" and 44" on long billets. I have a bridle from Draft Tack that is fairly good quality buy the reins were way too short. You need 110-120" reins. Not the normal 90".