So crazy it just might work

[Chainlube]

You could start with a 4x8 sheet of pink 2" foam insulation. Cut pieces and glue them together. (make sure it's compatible glue) A french bread knife and a sureform tool can be used to create the desired shape. Maybe cover this form with wax paper as a release agent and then lay fiberglass cloth on it.

Another good liner over the styrofoam is tinfoil. But the hard foam insulation is expensive, like Gordy says.