Over the years my lead has came from several sources. I used to work in an auto shop and with permission from the boss the lead wheel weights came come with me. The Snap on Man ended up with two huge rolls of lead, he was going to use it as weight, but didnt have a way to melt or cast it into the shape he wanted, so I talked him out of it. After moving on from the shop, my friends (techs) used to save the lead for me. As we all know times change and the last weights I picked up were zinc.
Currently, I have struck a deal with a salvage yard. I get all lead at current market price. It saves them hauling it and they get a fair price. Win, Win!!
Once I answered a news paper ad for lead at $.10 per pound. Ended up meeting a nice older lady and told her she was selling it too cheap, I gave her $.25 per pound. We got to chatting, she mentioned her husband passed and asked me if I could give her a value on some of his stuff. I bought a few other things as well from her. Reloading, casting and BPCR items. She listed most of it for sale and later called to thank me for helping her not sell his stuff too cheaply.
As for tin, I have bought bar solder at auctions for years. Typically doesn't bring much...
Lead is where you find it. If your having trouble in your area, let some folks know what your looking for and chances are you will find it. With any luck you will meet some good folks along the way.