I would definitely try checking amazon.

Yo Crf are you from Texas if so you may want to remove that link.

Not from texas but why risk it

crf's from seattle

Now I mus5 know, what was the link pertaining to?
Also you can try Etsy.com, but they might charge more. Ebay works too, but shipping could take forever.

I'd imagine making a cape isn't difficult and it would cost fifteen dollars at the most. Like, some snaps or Velcro, then all you need is the fabric (100% your choice) and you can decide how long, wide, flowy, and because its for the costume, receive even more awesome points for having made it yourself