So I had a fetch quest mission "deliver for Shauna", don't remember who gave it to me. Handed in the delivery bag and she gave me 21X Old Swim Trunks. I got it after she went home for the night so I went home, finished taking care of my animals, and went to sleep. Then I was just running around town first thing in the morning, went to the board and got some requests until her shop opened up.
I didn't even know this was an item in the game!