They have stick on weights and also magnetic weights now. How well do they work?....jury is probably still out. I have some of the stick on, but haven't really tried them yet.
I am merely a messenger here, I'm not your lackey to look up the sites that sell such items. 🤣
Wayyyy back, some heads would have a circle depression on the back of the head. You could then add a weight, or coin, or even a medallion of some sort. I have some of those weights still, somewhere. And a wedge with a medallion.