your best bet is to try your local steel stock holder. You dont show your location in your profile, it would be easier for people to advise suppliers in your area if you did. If you are in the Ayrshire area, Ayrshire Steel based in Ayr are pretty good for all sorts of material from RSJ's to wire mesh and everything inbetween! If they dont have 12g in stock they can order it in. i know at the moment the should still have alot of 10g 1" x 1" mesh in stock as I had a few sheets of it off them the other week.
