I've just found a company Vacuum Coatings Ltd based in London who will restore or make new front (first) surface mirrors at very reasonable prices. They are making a new mirror for my Thornton Pickard Ruby reflex which will be £16 ($25) which is very reasonable. I've opted for 2mm glass but they can supply 1.1mm.
They expect it to be ready by Thursday which is a good turnaround.
We used to have an engraver who made front panel parts for us. Whenever we asked him to make something he would say "it will be ready on Thursday". When we went to pick it up we were always told "I didn't mean this Thursday".