Is this the right foot well wall of the front passenger seat?
I would contact a local dealership and see what they can do for you, if not then search for a junkyard with a stang around your year and see if they will give/sell it to you. If that doesn't work and its REALLY bothering you, see if you can get some sort of plastic or vinyl to cover it.
That's all I can think of!
2006 JetWolf Gilbert, AZ. Come race me, I dare you. ASU!