Bumper Access Cover
 

Hi
Just purchased an 04 3.6L CTS. It did not come with the small access cover on the rear bumper. Can anyone tell me what this is for? Also where can I get a cheap replacement. I have shopped around and they range from $50 to $80. That is a little crazy for a small piece of plastic. I have also checked a couple of junk yards and no luck

Thanks in advance
Marc