If you Goggled Tin (SN) you know that there is only 1 - 10 not 110 , not tin foil or tin on your barn.
I would find it hard to believe that any junk yard would have scrap tin but if they do, that would be good.
Lead free "Bar solder" is Tin (SN) and Tin (SN) melts at close to the temp of lead if you are not using a thermometer. It will melt in your Lee pot fine.
Tin (SN) works great in a Lee Pot and pours very good. the spru is harder to break off.
The bad thing about Tin (SN) is the price. I use to buy it for $5 a pound and then all of the sudden everything in metals went sky high.