Need replacement SideView Mirror glass but cant find it

I don't know what glass shop you talked to, but exterior mirrors have no special requirements.
That sure looks like a Velvac to me. Try them and the local Chevy dealer.

If the mirror was flat any glass shop should be able to cut and fit a replacement. It isn't rocket surgery.
Do not try to use epoxy to hold the replacement. If you do use it and the mirror gets damaged again, you will have a bad time trying to clean out the epoxy to replace it.

Matt