Try scrap yards. That is the hard part. If you use wheel weight lead make sure it has not been coated. If you are using scrap lead you must clean it.

Put the lead in your pot and once it melts take a little bit of wax about the size of a peanut and put into your pot. Be sure you wear heavy gloves and use a long handle spoon. Stir the pot CAUTION the pot will flame up! Keep stirring this will bring all kinds of junk to the top of the pot. Take a smaller spoon and clean it off. Repeat the process. Now you should have pretty good clean lead.

Check out bassboatcentral.com and tackleunderground.com and do a lead search. You can find some great info over there.