Flight Suits makes the Gentex helmets to order. They also supply Gibson & Barnes hence why Flight Suits is cheaper. I remember mine was shipped in a way that it didn't incur import duty, so I would recommend Flight Suits. The Alpha Eagle is better and so is the MSA helmet that the Red Bull guys use but they cost a lot more.
EDIT: They're not called Flight Suits the place I was referring to is called Government Sales Inc.
Website.