I asked earlier about a suitable replacement for a door skin, on which the ply had delaminated. The a skin for the people entry door at the side of my garage, which is out in the weather.
I made various enquiries for sheets of new material, mostly plastic in the £70 to £100+ range sometimes I was warned that the plastic would expand and contract quite markedly - which might present a problem.
To see if I could do it some other way and a bit cheaper, I rang a couple of signage companies, with the idea of maybe scrounging some pre-used material from their scrap pile. One in particular suggested that they had a suitable plastic panel I could have for free, but better for the job would be some material they had which was an alloy/plastic/alloy sandwich, which was size stable and I could also have for free providing I made a donation to a charity they support. The full sheet is too big to fit in my car as is, so they are trimming it to size and I have arranged to collect it tomorrow.