Back in July I did create the extension, printed it on my 3D printer, and it's been on my car since. It's working great.

I appreciate the feedback that I must be tilting the mirror in too far. I know this is a common issue but do not feel this is correct in my case. With the extension installed and the mirror adjusted I stil cannot see the body of my car unless I lean. Whatever the case, here's the model:
https://www.thingiverse.com/thing:6401318