RE: Rifle Stock Needed: Winchester Model !00
Do a search on Google or Ask.com
Look on Ebay and Gunbroker.com....Also Gunsamerica.com.
If you do a search for Winchester Riflestocks I am sure you will find one. Most of the used ones are cracked or chipped at the heel from what I have seen.
Also, you can try GUNPARTSCORP.com they have parted out a TON of mod 100's. I bet they have one. (I looked, they are currently out, but they get stuff in daily, Price for good one is $93 if that helps you any)