All of my home stack vents are PVC covered in lead. Over the past few months the squirrels have eaten most of the flat lead and stack exposing the pipe and roof paper. Rather than making squirrel soup, does anyone know of a material to use over the pipes rather than lead that will keep the squirrels away or a product to cover them with?

You've never heard of the product called "Squirellbegone"? It comes in ,410, 16 and 12gauge. Use with caution!
But seriously folks, If this were my problem I'd rreplace the lead flashings with sheet metal. Good luck, Tom