One can be found in Chapter 1-3 on the roof of a cave before you meet the Merchant for the second time, along with many Spinels. Another one can be found in Chapter 5-3 inside Saddler's throne room just above the door you come in from.
Ironically, two of these treasures can be found in the campaign, despite the description of the headdress reading that its stone is "one of a kind."
- Hamamura, Koichi, ed (2006) (in Japanese). biohazard4 kaitaishinsho revised edition. Famitsu. ISBN 978-4-7577-2638-3.