Amazon.com : Manfrotto 501PL Rapid Connect Sliding Plate with 1/4'' and 3/8'' Camera Fixing Screws,Black : Tripod Camera Mounts : Electronics
Manfrotto 501PL Sliding Quick Release Plate with 1/4"-20 Screw at KEH Camera
Amazon.com : PM501 Manfrotto Type Quick Release Plate with Arca Swiss Type Clamp Built in Compatible with 501PL / RC3 / RC5 / NG Heads Features ProMediaGear Strap Port, for Video Heads