Copper is a finite material, but their is far more in a single world than one player could possibly need. Just scramble around the black forests and look for large mossy boulders that are speckled by a metallic sheen. They can sometimes be quite embedded in the ground so it might also pay to scan the floor.

The abundance and availability of certain finite materials has sometimes changed due to content updates, usually adding a new (but possibly still finite) source.