Maja, When I need a lead block, I make it. Over the years of metal
collecting, I have accummulated a bag of fishing sinkers, flashing,
etc. Simply melt the lead in a crucible of some sort, skim the slag
and pour it into a small tuna fish can or something similar. It is
not even necessary to remove it from the can to use the top surface.
Otherwise, just cut the can away.
If you don't have access to my type of source, check any plumbing
supply company...they normally have an abundant supply of lead
ingots....which by the way, can also be cut and used as a block.
Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut1