I thought it was door 6...Ah well, I can't remember.

Anyways, you can also get one on the Gaea Cliffs, climbing to the North Crater. There's a hidden room inside...when you're crossing a bridge over the entrance area, just keep running and you'll run through the icewall into a secret room. There's a ribbon in the chest.

Also, in the Special Battles at Battle Square. To get the Special Battles, you must win both the W-Summon and Omnislash items, and also have Cloud's Ultimate Weapon. Then, you'll get the option to have the Special Battles. You have to use Cloud. The...third enemy, I believe, is a Ho-Chu. Ho-Chu's are a helluva lot easier to morph than those Master Tonberries.