I'm assuming you mean X and Y, but you don't actually say.
Well ... Wild Horsea hold one as well. Lead with a Pokemon with Compound Eyes to improve your chances.
There is one lying around on the ground, however. It is in Terminus Cave. From memory it is not in the main area (the part where you catch Zygarde), but is in one of the nearby small caves.
Source: Experience and Serebii backed me up