Maybe just go back to "old" way and use sticky visoflex and iron on the shapes [drawn by you,from a picture] and sew around on your regular sewing machine. That way you can make them nice and large for such a parade. Will not need to be really perfect
Try Embroidery Library. I did some fall leaves from them a couple of months ago and I know they have maples leaves.
designs by sick has one that you might be able to use, it is in the applique leaf 5x7 collection. You will have to rotate it to sit straight.