I've been buying all my lead on e-bay by the 50-65lb box. The price of the lead plus shipping, import duties and exchange rate comes out to be around $0.13 per ounce, still cheaper than buying it locally. The lead can range from range scrap to pure lead from flashings. It's usually listed in the ads.
Check it out, search "lead ingots" on e-bay, lots of results and great prices.