The mirrors I have are plastic (acrylic?) with true mirror coating on the other side.
In original packing it looks pretty dull but outside and after washing with windex is not that bad. One of them was slightly damaged, and plactic was wrinkled on one place.. but for AU$1.00.... it is great.
I also found local supplier
http://www.acrilconvex.com.au/?gclid...FQv7agodTn7Pqw
but he wants AU$170.00 for quarter sphere, 470mm dia, a bit too expensive for my taste. It is also a bit too large.
I think the ideal size for the purpose would be between 150 and 250mm diameter.
EDIT:
some other links to local suppliers are below:
http://www.polite.com.au/pec_html/pe...FSEbagodaHoMrQ
http://www.convexmirrors.com.au/?gcl...FRwsagod6HC5qg
I imagine that side mirrors used for cars (retrovisor ? ) would also be quite OK