are there places that can duplicate a vanity mirror? or places to re silver an old mirror?
Assuming the actual mirror can be removed from the frame, getting a replacement custom-cut mirror shouldn't be too hard. Finding a place that can do re-silvering sounds more difficult and more expensive. It can technically be done yourself, but is probably more trouble than it's worth, and also requires removing the actual mirror from the frame.

Finding a place that sells custom-cut glass and mirrors would need to be done locally; this isn't an Internet type of thing.