Follow Focus Gear Rings (seamless flexible) for Vintage, Lens mod | eBay
Amazon.com : NEEWER Mini Follow Focus with A/B Stops, Lens Gear Ring, 15mm Rod & Rod Clamp for Cinema Camera, DSLR/Mirrorless Camera, Compatible with Lens Diameter Up to 114mm, PG001 (Silver) :
Pro Follow Focus Gear – Cordvision.com – Quality Filmmaking Accessories