Click on 'leaf' for a pic of the pin:
LEAF
You can make a very nice pin from shrinky-dink sheets that you can get at your local craft store. Follow the directions on preparing the sheet of shrinkable plastic, then put your prepared piece of plastic over a VERY large drawing of the leaf, and trace the outline of the leaf through the plastic. Use a foresty, bright green colored pencil to color in the leaf, then cut it out and bake it according to directions. You can then apply silver paint for the veins, and some very inexpensive silver colored wire for the looping stem and vine. Hot glue a pinback to the backside of the leaf and there you have it.
BTW - what will the rest of the costume look like?