Where does Stefan get his knobs?

Where can I get the knobs used in the photos for the modules? I'm building Sum Mix & Pan, Alstaden, Envoltura, Hans, Chasing Lights, Tryfelo, Natural State, VCA, and SVCA. I haven't used any ST Modular stuff before, but I was really impressed by the demo's and am an experienced builder so I went all out and bought a bunch of the PCBs and Panels. I have all of the parts, but I'd love to know where Stefan gets those knobs!

Thanks!