You could make your own alloy.

Melt down a few suitable bullets and cast them into balls. Put one at a time at the bottom of a tube about 4-5 feet long and drop a metal weight, such as a steel bar, down the tube. Do it 3-4 times and measure the indentation with a micrometer so you know what you grade of alloy you need.
I know it is not rocket science but if you amass different grades of lead you can test it and tell how hard or soft it is and take it from there.

Lead/tin solder is stall available on boot sales, and you can use wiped lead joints which are high in tin. It is a bit of messing getting the right alloy but any lead you have, or alloy, you can test the same way and use it as a guide to get the result you want.

Atb.