Question

About 15% of the people I trade with have at least 1 of them so I'm wondering where they get them

Answer 1

No you will have to migrate them or trade for them.

Source:Experience

Comments

.....;__;

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Don't forget that you can get them via the Dream Radar.
Source: http://bulbapedia.bulbagarden.net/wiki/Dream_Radar#Encountered_as_glowing_sphere

Answer 2

No, you can't, you must trade to get them, sorry.

Source: Experience