A couple vendors I know of sell them new- Mike Forte, (Forte's Performance parts), darn, went blank and had a senior moment on others....
You can find them on ebay, but they ask a lot of money for them.
You can look at other cars for them. I believe they came on the IRS Tbirds- 89-94, they also came on Lincoln Mark VII or Mark VIII, and some Cougars with IRS. You may want to place a "Want to buy" ad on the classifieds on ffcobra.com also.
Bob