I have never used push templates like that but i think they are not that hard to create. You probably could use plasticard and carve/file the shape of your cape in it. The big problem is probably the shape itself so that if wraps properly on the model.
Maybe you could use a sheet of paper as a basic cape and cut it into a fitting form, then trace it onto plasticard. Carve the area out and you have your own template.
If you want to go further - like sculpting folds into your cape - maybe this could be helpfull:
http://www.fromthewarp.blogspot.de/2012/06/how-to-sculpt-greenstuff-cloaks-and.html