Fun 3D papercraft masks/helmets - perfectly suitable for re-enacting key trailer moments while waiting in line!
Or, if you're less into folding and more into customizing - Walmart.com has these standard
Here's a sample of the Iron Man mask
As for the rest of the team?
Well, for Nick Fury - I did find an eye-patch template...
...but you're on your own for Black Widow, Hawkeye and Coulson.