OUTWEST1213
Would this be the forend/forearm screw that also holds the sling swivel in place as well as holding the fore stock to the barrel?? If so I have several of them. I have a small stock of them because the owners of many Win 100's had me swap out the originals for Uncle Mikes quick detachable swivels. That Uncle Mikes kit comes with a new screw that hold the detachable swivel.
So you can get an original from me or get in touch with Uncle Mikes to see if they still offer the quick detachable swivel kit for a M-100. Regardless problem may be solved.