Thanks, everyone. We actually ended finding exactly what she needed. Now, I just have to find:
1. green opaque man tights
2. Robin Hood hat - checking costume stores for that
3. archery-related gear - bow, arrows, quiver, one of those arm guard things
She wants me to be Green Arrow to her Black Canary, and who am I to argue, especially since she is sewing the top part of my costume herself. I think I may also carry around a copy of the New York Times and grumble about how bad black people have it these days (circa 1969).