Wintec saddles have a measurement system that you can easily change the size of your saddle any time you want. They are also synthetic and very comfortable!
Look for saddles with options to change out the tree. I know wintec and pessoa saddles have that option. Also, total saddle fit has a wither relief pad. I haven't tried it though
A good used Saddle by thorogood have high withered options. CWD is a higher price point but there are tons of uses saddles on the market that can accommodate higher withers without breaking the bank. Facebook groups are a great first place to look! Hope that helps!