Iron Man Helmet, suggestions for inner head holding thingy?

So, I have a mold of an iron man helmet, and I've got the faceplate hooked up to a servo with all the linkages and its working



The issue I'm running into now though, is that when I put on the helmet, the weight of it holds it in place, even if I turn my head. I was wondering if anyone had an suggestions on what/how I could put something inside similar to how bike helmets work to secure the helmet in place on my head and have it rotate when my head rotates (preferably with my head

Thanks!