Amazon.com : SIOTI 323 RC2 Quick Release Plate Adapter, Rapid Connect Adapter with Quick Release Plate for Man frotto Monopod, Manfrotto Tripod, or Other Ball Head and Tripod : Electronics
Manfrotto Hexagonal Plate Adapter - Accessory
Manfrotto 501PL Sliding Quick Release Plate with 1/4"-20 501PL