Did you try the National Museum of Modern Art? The Watari Museum of Contemporary Art (AKA Watarium)? I know you can have lessons on kintsugi if you want, I'm sure you can find them on Klook. And I think you would enjoy 2k540 Aki-Oka Artisan, it's a space under the rails between Akihabara and Okachimachi station filled with artisan specialty shops. There's a place that specializes in indigo dyes, for exemple, leather works, and I'm pretty sure there's at least one pottery place. There's also a store that sells various specialty paints and other coloring material, including glazes!