That gun may very well also share parts with the citori. Once you determine what part is needed it shouldn't be too much of issue finding it somewhere. I would check out Brownells.
Here is a link to a qualified gunsmith.
HE actually wrote some of the books on gunsmithing. If the early Citori and Miroku are the same or similar, he should know how to fix yours, as he was the west's Browning warranty repair for many years. He gets the work done and doesn't "store" your gun for several seasons like many other gunsmiths.
http://www.piscogunsmithing.com/