Hi, Your 515 20ga was marketed and sold as Stevens/Savage ,Springfield and a fox line. You might try eBay or some of the stock cutters around. One of them may have a pattern. Silver hill cut a stock for me last May and did a good job. When I look at the action 2 things look familiar. The first is the action. It looks like a 311 base and since it was sold as a fox model also a fox stock may very well fit. I have not been a lot of help but you now have some where to look. Several vintage gun parts houses are Jack First gun parts and Bobs gun parts. Good luckJted