There are no available kits to make your airsoft gun look anything like a gun from Halo. If you're going for accurate details, an AUG, F2000, or FAMAS would be your best bet. A customization company is attempting to make a TAR 21, that might provide a better sized base. Personally, I'd like to try an AUG (Version 3s are supposed to be easier to work on than V2s anyway), and essentially cut up the original body, creating a new mag well to have a more accurate magazine (Not to mention the price of AUG magazines is pretty bad, especially on midcaps).