I need to replace the side mirror cap which cracked when the car was backing into the garage and hit against the side of the garage door. The pieces circled in red are the cracked parts.
Has anyone replaced the mirror cap before? Is it possible to replace the parts without removing the door panel to remove the whole side mirror assembly?
Thanks in advanced for any feedback.

 

^
I suppose you could try?
The below is all I could find related to the parts you have circled above.