What to use instead of coroplast in a c&c cage for a guinea pig?

I already have the cubes. No sign stores near me that sell coroplast that i could use. Ive searched everywear no one has it and I cant buy online. What can I use instead of coroplast for the bottom of the cage? I would be useing Fleece as bedding if that would help at all. please any answers would be appreciated.