How do you obtain a Custap Berry in Pokemon X/Y?

Question

I saw sites mentioning that it exists yet none specifically detail where it is. Some confirmation would be greatly appreciated.

Answer 1

Custap berry is unobtainable in X and Y
Source

Comments

Cutsap berry is in the game, other Pokemon have it. With thief you could obtain one, but the only Pokemon I've seen with it are in places that you can't keep the item afterwards.

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Then you can't obtain them