I bought one of the Mk42 Disguise helmets from Amazon for less than $20 shipped. It's actually decent at that price, though I wouldn't touch it at $40. The dimensions are proportional and most of the key details are there, but as people said it's thin cheap plastic and a 2-piece design secured with velcro. I think if you just need something fast and are willing to put a little extra work into it, you can actually make it look a lot better and stay within your budget. I bought this knowing I wasn't going to wear it, I'm just going to carry it around. I got it as a cheap throwaway Halloween prop piece to go along with my Tony Stark Mk42 mech test costume this year.