What Cayugad said. Midway has pure and alloyed about as cheap as the average guy can order lead. The new flat rate USPS boxes help a little on cost but it's still high. Plumbers lead or old sheet lead used for roof flashings are both good lead. If you live near a shipyard they probably have scrap ballast lead which should be good stuff. If a nearby hospital/medical facility does any radiological work, they might have a pile of the stuff (I doubt it,but worth checking) from any prior equipment changes. Ya gotta get creative or pay a bunch for it.

Seafab.com will sell direct but they have a pretty high dollar figure on the minimum order. $500 I think.