Hot Shoe to 1/4-20 Thread Male Post Adapter Mount for Cameras, Rails, Ball Heads and Flash Connections - iShot Mounts
Amazon.com: JJC Male 1/4"-20 to Female 3/8"-16 Threaded Screw Converter Adapter for Mounting Camera and Other Devices with Female 1/4"-20 Thread to Tripod, Monopod with Male 3/8"-16 Thread or Arca-Type Clamp :
GoPro 1/4-20" Adapter
Amazon.com : Standard 1/4"-20 Female to 3/8"-16 Male Screw Adapter Reducer Bushing Converter for DSLR Camera Camcorder Tripod Monopod Ball Head Ballhead Video Light Stand (4 Pieces) : Electronics
Noga 1/4"-20 x M6 Adapter NOGA-AD6010 B&H Photo Video