When I was 'into' Gallery Glass painting (see examples submitted in photo comp)
Competition # 22 - Accrington Gallery
I bought sheets of clear perspex from a works near the junction of Nuttall St and Victoria St.
I still have one piece of clear perpex which I intended to use as a 'triple glazed' unit for a fanlight at the address I left 7 yrs ago.
It cost me about £30 then but I have not found any use for it where I live now.
It is stored in the deep recesses of my landing storeroom so I have not measured it before posting.
I recall it may well be about 3'x2' - and is still preserved by its peel off coating, so I don't expect it will be scratched.
You can have it if it will serve your purpose.