Are you talking about the metal bezel on the front that surrounds the screen? If so, I don't think you can replace it. From what I understand, HTC uses a metal unibody construction, so that metal bezel isn't a "piece", it's intergral with the body of the phone. If it's scraped up you may be able to paint it or use a black permant marker to clean it up.
Also, "Please help" is not a descriptive post title. Something like "Need help replacing the thin metal piece around the perimeter" would be a lot more descriptive and would attract people who actually know something about the topic.