Jim, I've been told you can buy cotoneaster seedlings from Musser Forest in Indiana, PA. I got this info from a nursery in PA. Good Luck on your project. Best And Happy Yardening, Nancy.
Sorry Jim, I was told they did by a nurseryman in PA. Did you find them? If so, please share your source. If not, I suggest you contact the PA cell of the Conifer Society. Best Nancy