Ebay, How deep is your pocket? How long can you wait, a year, 3 years, 5 years?
Almost impossible to get hold of. When you do manage to find one, You won't be the only one after it. Expect a full out bidding war. I haven't seen one for sale for quite some time.
If however you don't mind an aftermarket cumstomised one, along with the paint code tag. Monster on the RSOC forum does a brilliant set he can make and sell you. Don't know how much these cost, I had a set made up 5+ years ago and cost me £35.
If not you can go to Ford and they can make up a black VIN sticker for you?