Now that I have a little time.... Links.
ISSO Sidesaddles for Sale
Hundred Oaks, Inc.
I bought my previous saddle, an Elan, and my current saddle, a Steele English Pleasure, from Hundred Oaks. The English Pleasure is a great saddle--NOT a pretty saddle by any means (the Equitation is a much prettier saddle), but very comfortable and I *love* the western bar tree.
I just bought a restored Western sidesaddle from ISSO. They did a fabulous job restoring it. It's beautiful...and completely safe and ready to ride.
Good luck on your search!