They have some polygonal magnetic tiles that you can assemble into geometric solids at the Omaha Luminarium (like the Bay Area's Exploratorium). They're fun to play with — perhaps you could make all the Johnson solids with them.

I'm having a hard time though finding a set you can purchase. Something called MAGFORMERS was the closest I could find on Amazon. Most similar products consisted though only of squares and equilateral triangles.

Of course you could easily 3D print these — leaving a void along the center of each vertex suitable for inserting a long cylindrical magnet (which is how they generally appear to hold together). It's hard to be a the look of injection molded plastic though. :-)