I'd suggest to look into Thorowgood, Thornhill or Duett. Your horse does look pretty wide and those brands are quite targeted on wider horses. If you don't have saddle fitter in area (BTW, where are you approximately? may be someone on forum from the same area and can give some suggestions) work with the store that allows trial, so you can see the fit. You can always take some pics of the saddle on horse to get some opinions/critique on fit.
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