i made it using a bench grinder to bring out the basic shape and create the bevels for the edges, heat it up to cherry red and fine tune any malformed hard to grind areas.
I don't have an actual pattern but i can give some step by step instructions.
1: get a flat piece of steel preferably 6 inches in length in case you mess up the initial grinding.
2: mark the center of the piece with a marker or anything else you can clearly see
3: draw out the outline of the wings coming in 2 inches at top then curving down till it comes in 1 inch, making a point coming back out. (remember the bat head)
4: make another curve coming in towards the center to form the second part of the wing plus the tail
5: at the top make some bat ears try to make the the same height as the top wings
6: do the same thing on the opposite side
7: I grind to shape but if you have a cutting torch then by all means I just can't afford anything else
8: if desired bring it up to a dull or cherry red to finish the shaping.
9: heat up the piece till critical then quench in motor oil (if you want a black finish), if you do not like the black then polish.
10: congratulations you now feel like bruce wayne and want to go kick some bad guy butt, remember if you do and you throw this at someone you didn't hear how to do it from me