I doubt very much if you could buy just the E. Maybe at a junk yard. I think if I was in the same boat, I would strip the rest of the letters off and go without the Crossfire logo across the trunk. That looks pretty good. There's a post on removing the logo. You could put Andrew's Crossfire emblem over the Chrysler badge on the trunk like on my sig at the bottom of this post.

Of course you could always contact Alex Trebeck, I've heard he'll sell you a vowel.