Designer fake helmet? Interesting.... so you're a clothing designer that wants to find a safety-item spin-off product? Have you thought about maybe fake mountain climbing harnesses? Or pretend hearing protection? Maybe non-functional eye protection?

I am no designer myself.... but I think I'd start with designer [fake] safety shoes. Maybe use a simple foil in place of a thick steel... as a replacement for steel-toe shoes. Not that toes aren't important. But compared to brains... maybe less important.