There are plenty of companies making varying weight cartridge screws to start with.
A friend has some on his table where the head of the screw is a large brass knob shaped afair which added a decent amount of weight.
Myself I machined a piece of brass to fit top of headshell with two holes to enable screws to pass through.
Yes you then likely still would need longer screws.
But as a test first a tiny bit of blutac with a penny or dime on top of headshell and see if it even helps before going any further.
A friend has some on his table where the head of the screw is a large brass knob shaped afair which added a decent amount of weight.
Myself I machined a piece of brass to fit top of headshell with two holes to enable screws to pass through.
Yes you then likely still would need longer screws.
But as a test first a tiny bit of blutac with a penny or dime on top of headshell and see if it even helps before going any further.