Waveguard cover replacement material

I got hold of an old Whirlpool AVM541 microwaveoven,

The waveguard cover is damaged and I want to replace it.

Can I use an ordinary cardboard (like a frozen pizza container) plate that i cut to size?

I understand that a sheet of mica will last longer, but the cost of available cardboard is zero, and mica is hard to find here in Oslo, Norway. Whirpool will sell me a replacement cover for 227.- NOK equal to roughly 22$. Thats way to expensive imho.

God bless you in Jesu name.