You can probably go to a costumes store or order them online.
yes
Of course there is. Google is your friend.
yes
I always check toysrus.com because they show some master chief {halo 3 editon} costumes but i can't say that those things are cheap.
You can get them on eBay but they are dear about $50
game traders lol:)
You can buy children's halo costumes from Party City. They can also be purchased from Amazon and Costume SuperCenter.
Halo 4 is called Halo 4.
Halo rights are owned by Bungee. Technically Halo 4 is "Halo ODST"
There is multiplayer in halo 4
Yes, there is a Halo 4.
there is no halo 4 because it is a trilogy. halo 3 was the end of the series.