Make a framework from wood to fit over the table and cover with a wire mesh. the type that you see Rabbit and guinea pig enclosures are made from. You could either have it hinged so it sits on the top, or so it fits over the sides of the table. We dismantled an old guinea pig run to reuse the panels as a lid for one of the outdoor enclosures. It stopped next doors cat getting in. We now have bigger enclosures with their own meshed lids.

Your local wood yard would be able to cut it to size for you.