Track of the Wolf sells good Minies but they aren't cheap.
For the cost of a Lyman lead melter pot, a mold, and 60 lbs of pure lead from Buffalo Bullets, you can be casting these for $0.16 cents a piece vs. buying from Track for about $0.60 shipped.
I don't cast but if I had me a rifled musket I'd certainly take it up if I was going to shoot it a piece. You'll save a lot of money this way!