Plenty of suppliers either on line or local. Worth shopping around as prices vary. From memory it is 8mm smoked. I have always used a local signmaker and expect there will be one near you who will be able to machine it to size, finish the edges and drill for the lock. Worth considering splitting it horizontally 70/30 with a downward facing cut and a teak baffle over the join. fitbarrel bolts to the lower part and it can act as a baffle to keep water out - comforting in the rough stuff when water can come into the cockpit. Makes the washboard easier to handle as well and if you get the split right you can still stow in the brackets in the aft cabin. One of my better mods on my 37.