hi guys,
I little bit help needed

I'm trying to figure out how to connect the head to the body with a plastic/rubber material (i don't know yet) but the main problem is how to make it Linked to the head.
ex. When I move the head the part of the part (new one) witch is connected to the main body will be in the same place and the part connected to the head will move with it. But I need it to move like a rubber/plastic material. if it goes smaller it shrinks visibly if I stretch it it stretches accordingly to the movement.
I attache some pictures, hope I posted a question in understandable matter.
Any help will be appreciated.