Mine are plywood and starting to flake at the edges, and look grotty. Does anyone sell made to measure replacement doors and washboards in perspex/polycarbonate, or some such stuff?
Look up yellow pages for signmakers, signmakers cut shop front lettering from large sheets which are just under half an inch thick, if you take along your washboards as template the new bits will fit. If you are in West of Scotland I can give you a name in Ayr.