I make my buttons from polymer clay, which is a modelling clay that is baked in the oven to harden it. It is strong, lightweight and washable. You can machine wash them, though I would not recommend using a hot wash, or hot tumble dryer.
Most of my buttons are one of a kind designs which cannot be exactly repeated, though in some cases I can make similar designs in colours, sizes and shapes of your choice. Do contact me if you think I can make buttons for your project. I may be able to match your yarn or fabric colours. You can contact me on Etsy, or via the contact form on this website.