Ralph Moore Auto Galss at Mascot seems to specialise in glass for older cars. He is located quite close to Mascot station so you could catch a train if needed.
His number s are (02) 9667-1933 ; 96691628.
I have not used the company so I can't speak to how good it is.
Although I did call in there some time ago and seem to recall they had quite a few concours condition cars in there having work done on them
Hope that helps.