Mysterious items in Star Ocean: The Second Story...

There are a few items in this game that have really been bugging me for a while now.
Either they have a "no known location" or are thought to be dummied out items, but I'm 100% sure I've seen a few of them in the game before.
I remember I managed to make Original Boots and Odd Shoes with Opera and Ernest a year ago (through failed weapon Customization for some reason);
there's also Ashton's Flashy Armour, an item that is listed everywhere and that I'm almost sure I have created once, but no matter how hard I try I can no longer make it, no matter what Ashton's level or his Customize level is;
and then there's also Odd Medicine and Odd Helmet...

Does anyone have any in-depth information on this?
Because as a perfectionist I feel rather paranoid when all characters might miss their shots at their own unique low-level failure items just because I leveled them up too much.

I've heard you can get all of these items from Treasure Chests and/or Santa's Boots, is that true?