Maybe one of these similar products would be of interest:-

Leg Extension and Curl Machine Adjustable Leg Extension Attachment Seated Lower Body Special Leg Rotary Machine Leg Extension Rack Attachment (Hole Diameter 18mm)

EVERYMATE Leg Extension and Curl Machine, 3-1 Adjustable Leg Extension Machine, Leg Curl Extension Machine for Lower Body Workouts, Leg Machines Home Gym - Heavy Duty 680lbs Capacity

Bowflex Power Pro XTL Leg Extension OEM Attachment w/ Safety Pin Free Shipping

Bowflex Ultimate 1 Leg Extension Attachment Foam Rollers Pulleys Cables OEM ????

1 Bowflex Leg Extension Foam Rollers Power Pro XTL Replacement Part