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) :
Lux Gears Review: Are these the follow focus gears you've been looking for? - Newsshooter
ZEISS Lens Gear | Attached in a flash
Wide Open Camera Focus Ring
Wide Open Camera Universal Lens Gear 605859 B&H Photo Video
Tilta Seamless Focus Gear Ring (56 to 58mm) TA-FGR-5658 B&H
Amazon.com : SmallRig Seamless Focus Gear Ring (72mm to 74mm) - 3293 : Electronics
LENS FOCUS GEAR RING
LanParte DSLR lens fine turning follow focus Gear Ring-Dongguan Lanparte Television Equipment Technology Co.,Ltd.