This:
https://www.amazon.com/Action-Replay-Powersaves-3DS-2018/dp/B07BM9XXB7/ref=mp_s_a_1_3?keywords=powersaves+3ds&qid=1558872646&s=gateway&sr=8-3 , is the easiest way to get your event items, if using this, you should probably save state your game first just in case your save file gets corrupted.
It only works with: Heart Gold, Soul Silver, Black, White, Black 2, White 2, X, Y, Sun, Moon, Ultra Sun, Ultra Moon.
