Almost any 'Glass Merchant' will be able to supply it.
Ask for > Astari Niagara International, cast acrylic sheet, Colour = 101, RED or 103, RED which is a shade lighter. They are clear/see thru if you know what I mean. Not surface coated/coloured.
BUT, it's been recommended to use GREY film, alah..car sun screen/solar filter which can be obtained for free as offcuts & works much betterer at cutting out the white glow without losing the ability to 'read the screen'..
L.