Sliding Quick Release Plate, Cayer QR120 Universal QR Plate Replacement with 1/4 inch and 3/8 inch Mounting Screws for K3 Fluid Head for Manfrotto 501 500AH 502AH 503HDV 504HD: Amazon.co.uk: Electronics &
SmallRig Quick Dovetail Base Plate for Manfrotto 501 Tripod Fluid Head -1280C | eBay
500PL Standard Plate for 501,5 - Park Cameras Online | Park Cameras
Bexin Quick Release Plate Adapter Mount Sliding 501pl Rapid Connect Base For Manfrotto 501 503 701 Q5 Camera Tripod Accessories - Tripod Monopods - AliExpress
SmallRig Quick Dovetail Base Plate for Manfrotto 501 Tripod Fluid Head 1280C | eBay
CAMVATE Quick Release Mount Base QR Plate for Manfrotto 501/504/ 577/701 Tripod Standard Accessory(Red): Amazon.co.uk: Electronics & Photo