When Riku gave Kairi a keyblade to fight with where did he get it from

He probably created it himself, but im guessing it's not a really special keyblade like Mickey's, Sora's, or Riku's. Why I say that is because when she uses the keyblade, and you finish the fight against Xigbar (Xiggy lol =]) Kairi's keyblade disappears and she never has it in the game again.