Replace Roof Marker Light

I just purchased a replacement roof marker light (passenger side) at my Hummer dealership and paid $85 for the part.  This included the wiring and light, as well as the amber plastic cover.  All I needed was the amber plastic cover as it was damaged going through the car wash, but they do not sell them separately.
 
I realize I can find different styles and replace all of them but at this time, I only want to replace the plastic cover.  Before I install this part, does anyone know of a location to purchase this amber cover only at a more reasonable cost?
 
I have searched the Internet for the part number but no luck.
 
Thank you in advance for your help.
 
Bob

Put it on and dont use carwashes anymore....

Looks like you are going to have to use the one you bought