There used to be a firm that was able to produce laminated flat windscreen glass in Leeds. They were situated the other side of the ex-railway viaduct, near Dunelm at the Armley Gyratory. I forget what they were called and they might not exist anymore.[it was quite some time ago] Maybe Dr Google can help
Be careful what thickness you get as glass, like so many things, now comes in metric sizes. I don't have an L but the J was 1/4 in which is 6.36 mm. You may want to use modern laminated glass and most glass places should be able to cut this for you. Be mindful that as well as the glass itself there are various soldered on parts for fasteners and/or wipers inside which have to be accommodated with cutouts to the glass and the cutters may not be able, or willing, to cut round these. In addition the rubber channel can be problematic with many ingenious solutions to be found in the archives. Good Luck. Ian
I use Dorset Glass Co, Bournemouth. Laminated. Fixing with Geocel black rubber gutter sealant. If you want to do it yourself, email me, maybe I can help. I have done many screens. Nick.