I guess 3M should be your first port of call. It depends on what a ‘serious amount’ means. If they won’t sell direct to you, they will at least give you the names of their major suppliers. As a guide, I seem to remember 50 metres @ 610mm being about £3500
Edit: There are other class 1 materials: Avery do one, also Reflexite and Nikalite.
Please note:
This action will also remove this member from your connections and send a report to the site admin.
Please allow a few minutes for this process to complete.