Hi - just joined this forum and realise this is an old post, but recently dealt with a mirror issue for an old Astra.
I contacted these guys in QLD sales@mirrors4cars.com.au and they make mirrors to suit all cars. Cost seems reasonable too compared to dealer products, at least it was for Holden.
I had a mirror glass on the Astra slide right off the backing plate in the summer heat while I was driving! I didn't end up buying from mirrors4cars, and instead made my own from 3mm mirror glass, a $5 glass cutting tool, and a hell of a lot of sanding, and it reasonably fits my Astra. But Pete from mirrors4cars was very helpful to me even though he knew I wasn't going to buy from him unless I botched my DIY job. I wouldn't hesitate to call him if I needed another mirror, or if I can't get used to those damn convex mirrors in my new i30.