So lead has become a truly precious metal.
Maybe we can use silver, like the Lone Ranger, or depleted uranium, which packs even more of a wallop?
The value of a lead slug is that it carries a great deal of kinetic energy. The larger the caliber, the more damage it does.
But a very small caliber slug, at sufficiently high velocity, and even of non-lead composition, can carry a sufficient punch to do at least as much damage. A .223 Magnum (4,600 fps muzzle velocity) is not a varmint gun.