Mustangs unlimited page 79 part # TRA656101. Exactly what you are looking for. Its a 5 speed conversion knob. Looks exactly like the black dished knob with the chrome bottom and the 5 speed pattern engraved into it. It aaalso comes with 2 thread sizes!
www.mustangs unlimited.com
http://www.mustangsunlimited.com/images/TRA656101-B.jpg