itch.io

If you read the books in the Agranor library, you usually won't have such problems, as it's known that most of the necessary resources are available in the locations where Celica carries out her work for the guild.

The locations you find items like this are from the limited treasures from exploring, and the random presents from the shop. I'm pretty sure there's exactly enough stocked to make all the clothes.

As you progress through the story to the part where you visit the hot springs—and Kimiko mentions that some fairies are playing a trick on you when you ask your fairy friend to take you to the "fairy village"—you pass through a place called the Willow Forest. There, you obtain the two enchanted threads by exploring and opening the two silver chests needed to complete the witch outfit.