I feel your pain, I have been on the hunt forever it seems. I bought a red plaid swing coat from victoria's secret on impulse last winter. Sadly I haven't came up with an original outfit to pair it with yet. I need a real cape.
Trust an Olsen to pull off something only ever seen on retirees in Florida. And pantsless no less.
Capes are really REALLY easy to create though. I'm sure any local seamstress to you could whip up your dream cape if you can find him/her the materials for it.