In normal circumstance Formers are made from mild steel.
If you have not tried it i SUGGEST YOU TRY corian. This is a Dupont Pastic used extensively for kitchen worktops. The sheets are approx: 1/2" thick. Any kitchen fitter will have offcuts from letting in Kitchen sinks etc, and will charge pennies for them. If you need thicker than 1/2" it is a simple matter to gently sand the face, coat with Supoer glue, and clamp.
They are really easy to cut, and grind to any shape.
Try it …Uou will not be disappointed…..Good luck
Malcolm Farrant