There are different ways to look at this design. First of all, it’s a tribute to the ubiquitous, and lovely, hexagonal colour pencil.
It’s also a representation of a new internet-friendly production model: combining relatively simple, locally available materials with high tech, custom designed interface parts.
Combine the central connector piece with any set of at least 36 standard hexagonal pencils of about 7.0 mm cross section (measured at the smallest diameter), which are available around the world from many department stores and art supply stores - I’ve seen good sets for as little as 5 euro.
You can also use branded sets; examples of pencils that fit are Stabilo Aquacolor 1600, and Caran d’Ache Prismalo I, but there are many more. Normal graphite pencils often have the same size and shape and work as well.