So it's no surprise that this has been done by me really, I'm a huge Arkham fan so this was inevitable. I got Batgirl ages ago so a few days before t arrived in the mail I bought some black nylon (umbrella material) and gold cloth, then I sketched out the shape based on the plastic cape and pictures arm span in relativity to wing width etc, made a cardboard template, then sewed two bits together cut them out used an iron to shape the cape ridges, inserted a wire in a gap I left attached the bat broch, used miliput around the neck to keep it in place and fill the gaps, glued down areas and then gave her a repainted. It's come out well. Did some fun scenes etc.