Don't know for sure, but have you tried contacting a masseuse? Obviously they won't want to get their hands dirty (haha - no pun but maybe they can recommend some professional massage techniques that can be applied to the sphincter and/or muscle group(s) that affect the sphincter.

No luck with a masseuse, then contact your local pharmacist...they've seen it all, they've heard it all. And they're highly trained. Have them make a recommendation. Even if you have to get a Rx, at least you'll have a drug name to tell your doc. Most medical MD's are frigging clueless to shy bowel issues.

For what you are looking for, I hope this helps!