how much would this cost?

You mean like artwork? It's all up to you. Too much and nobody will bother, too low and you'll be wasting your time. Just be fair.

I dont really like many of the aftermarket front bumpers for the Z... Or I like a little from each of them, but none I can really decide on. So i figured Id design my own, and find someone who can fabricate it. I am just wondering how much that would cost. I dont plan on selling them. I just want one so my car could be one of a kind.

How good are you at scuplture??

If you can make what you want out of plaster or cut it out of foam, making your own fiberglass mold is easy.

I suck at art, so this isn't ever an option for me, but maybe you???