I bought the whole set (because it's pretty much my favorite) except for the shorts, which are nowhere on the shop OR gallery search. I don't know if people do this, but does anyone have the shorts available for a quick lend to get the achievement?

There is a thread here https://subeta.net/forums.php/read/5832/Borrowing-Lending-for-Achievements where people lend and borrow items for achievements. Good luck!

I had no idea about that thread, thank you! :D

You're welcome!

I found a lender, so thank you again!