If you are near farmers or farm equipment dealers try to pick up some small tractor wheel weights or tractor front end weights. They are made of cast iron.
I pick up a small one about 18 in to 2 foot dia, weighed about 85 to 100 lbs.
Cut it up on my 4 x 6 band saw Very Carefully. : Cuts like butter,
even better tham some window sash weights I have. Enough material for several years projects. Paid $20.00 U.S. for mine.
I cut off a 3 in arc of it, as they are round, and got 4 cyl block blanks out of it for Bogs
Paddleducks engine.
Ron