Lead is going to get hard to find everywhere someday, I'm afraid. I cast bullets and will never have enough. It's being phased out of tire weights. You can buy it off ebay for as little as about a dollar a pound sometimes and you really get your money's worth with those flat-rate shipping boxes! Roto-Metals has the best prices for virgin alloy if you feel so inclined and often runs sales.
Don't know what you're doing, but pure lead will be soft and be more difficult to get good fill-out if you're casting and it matters. Clip-on wheel weights are a pretty easy casting alloy and are a good compromise and are even heat-treatable if you need them harder. Keep an eye out for pewter at yard sales, etc. as it can be used to increase the tin/antimony content of lead alloys if needed. Lead shot contains arsenic, though I'm not sure it would pose much of a threat. Car batteries are alloyed with calcium and marine batteries are alloyed with cadmium and should be avoided. You may also consider using zinc if it may be easier to find. Don't get zinc in your lead! If you have any questions about lead melting or smelting, feel free to PM me if you don't want to post it.