Call Slate Run Tackle; I would have some grey fox, along if I were you. Its kinda like a March Brown you might find some of those too. Slate Run Tackle Shop
I used to fish it a lot and did the best fishing a #18 or #20 Blue Quill with real slate gray quill wings during the March Brown and Grey Fox hatches. Don't know why but they would take that little fly floating right in the middle of the big real flies. If you don't tie quill wing flies The fly shop in Waterville Pa. has nice ones that they tie on site. McConnell's Country Store and Fly Shop, Waterville, PA
You probably won't use the #18 blue quills like I'm telling you to because I don't own a shop. I would if I were going up there to fish. I always caught more fish than the guy behind the counter who was telling me how.