I believe there are three.
The first one you can obtain is in the cubicle where Aeris and Red XIII were being stored in the Shinra Building on the 68th floor. You have to beat the HO 512 boss beforehand.
The second one is in the Forgotten Capital. It's in the shell house on the east side where there are beds you can sleep in. I think it's just above the furthest bed.
The third one can be obtained if you visit the Chocobo Sage's house. Examine the green chocobo he has stabled and it will drop it.
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