Link stone or trading?

ive got a few pokemon who id like to evolve, who only evolve through trading. in reborn, theres the link stone, which was referenced early in insurgence, but ive finally made it to the department store, and cant find it here, so im thinking it might not be available. can anyone tell me how to do this?

IIRC, the stone referenced early in the game was the IV stone.

However, there is an NPC called the Witch Doctor who evolves pokemon that evolve by trading.

thankyou very much!