Courbette eMotion tree in XW is another.
Do a wither tracing. Cut the shape out of cardboard to take with you to tack stores. You'll just have to eyeball the curve (or "table" lol) of the back and compare the saddle tree to that. http://www.yourredwagon.com/Degree%20Method.pdf
can be used with photos, to some extent. Usually a horse that's wide in the front will be wide and table-backed all the way back, but there are some exceptions. We discussed the Wintec cc trees, and how with the XW, the gullet might fit but the tree is too curvy for the wide horse. Their "new" dressage and AP models 500 and Pro and Isabell (since 2010?) are a straighter/flatter tree than the past series of them that are currently sold as the 250 series.