I got a set of those on craigslist a few months ago. There was a set a couple weeks ago on SVTP, might still be there? You could also try searchtempest to see what comes up within a certain radius.
2014 Grabber Blue Mustang GT Premium with nav, RR and comfy packages, 3.73 limited slip axle and optional 19" machined aluminum wheels. Come hang out in the garage and check out my build so far!