Just as a postscript, a very kind US reader of this group sent me some suitable pads, and refused any reimbursement. I won't name him, of course, but would just like to say a public thank you.
They were of a different make to the originals so have given me a pointer on getting supplies of these for other owners of my car in the same position - I'm a member of a one model car club.
They appear to have been etched from copper clad Kapton sheet then laminated with plain Kapton giving a thin and flexible but strong insulated element. I'm hoping it might even be possible to make my own using conventional PCB techniques, if I can find a supplier of smallish amounts of this, or similar, material.