Feh. So the news article says he's using industrial grit. The presumably more authoritative arXiv paper states
The ball lenses used in constructing Foldscopes included material types borosilicate, BK7 borosilicate, sapphire, ruby, and S-LAH79. The vendors included Swiss Jewel Co, Edmund Optics, and Winsted Precision Ball. Part numbers for some select lenses include: 300m sapphire lens from Swiss Jewel Co. (Model B0.30S), 200m sapphire lenses from Swiss Jewel Co. (Model B0.20S), 2.4mm borosilicate lenses from Winsted Precision Ball (P/N 3200940F1ZZ00A0), 300m BK7 borosilicate lenses from Swiss Jewel Co. (Model BK7-0.30S), and 1.0mm BK7 borosilicate lenses from Swiss Jewel Co. (Model BK7-1.00). Note that half-ball lenses from both Edmund Optics and Swiss Jewel Co. were also tested for use as condenser lenses for the LEDs.
So they aren't exactly industrial grit, but very tiny lenses that look like they were originally intended for the telecommunications industry. The question of how does one get these lenses is answered by, "pick up the phone and call one of the listed suppliers who specialize in micro-spheres of clear, hard stuff."