I maybe able to help. I work in the scrap industry as a labourer. Every scrap yard is different some aren't open to the public and others its not worth their time to sell to the average joe. Most will have a junk corner where all the odd ball stuff sits for a while. I'm talking every kind of lead alloy even dross. Like McDonalds scrapers make pennies so volume is the only way to get them to part with their material be prepared to buy a hundred pounds. Lbs yes. Wheel weights are a waste of time because they're heading in a lead free direction. Steel, zinc and plastic weights are becoming more prominent. Want hard bullets ask if they have a "hard lead" category or simply list the recipe you're looking for, they might have sn/pb solder spools, pewter or babbit kicking around. Give them a call. The price point is going to be the price point, they aren't making money selling fifty or a hundred pounds at a time when a single completed container weights 3,800 to 5,500 lbs. Often there is a "soft lead" category which will work for you muzzle loaders.
cadmium is toxic.
They want the business and their phone numbers are out there. Phone ask, make a deal.