You could go to ebay and get lead. You could also go to Track of the Wolf and get a Lee mold and melting it, well if you have an old cast iron small pot or dutch oven and melt it on a propane stove or a melting pot from Track too.
As a word of caution, casting is highly dangerous and burning yourself is almost normal. Watch out for ANY moisture or even bugs. They will make the lead splatter. If you know someone that does their own, learn from them. That is the best way.
Have fun.