Where can you get NFL GU stuff like the old J.O. sports?

[War Helmets]

I remember J.O. sports from a few years ago,but I wasn't collecting then.I am looking for a Raiders helmet & some what nots.Where do NFL teams sell stuff?Is it all on NFL.com auctions

[War Helmets]

And does anybody know who has the contract on Raiders game used equipment.Don't want to buy out everything,just need a helmet