You need to learn how to ask: Hi, My name is Bob, I am preparing some items to take some kids hunting and fishing. I was wondering if you had some used wheel weights that I could have to melt down?
Don't lie. Offer to bring by some cast bullets, or some fishing weights. Once they see what you are making, you will likely have a life time supply. Then take your kids out shooting and fishing.
You would be suprised how fast Wal-Mart and some of the other places will donate if you are using the items to take your kids or grandkids into the outdoors.
Buy a few fishing weight molds also. They are fun to cast (in a couple of ways!).
Steve