How do you get Orichalcum kh2?

You obtain Orichalcum by opening chests in Kanga's House and the Spooky Cave in 100 Acre Wood, Throne Room in Land Of Dragons, Ship Graveyard Seadrift Keep in Port Royal, Underground Concourse and Tunnelway and Mansion Library in Twilight Town, Fragment Crossing and Nothing's Call and Naught's Skyway and Ruin and Creation's Passage in The World That Never Was.

Also Bulky Vendors carry them and you may be lucky enough to get one if one appears.