This part has been discontinued.The manufacturer has replaced them with one of the following depending on the model lift chair you have:
Global Lift SKF Actuator
Price: Discontinued by Manufacturer
Muriatic Acid
Price: $35.70-$2,648.68
CLAMP KNOB
Price: $19.77
Landscape Slide RT17
Price: FREE
Tri Point Anchor System for C-375/C-450
Price: $549.58
Retro Fit Anchor System
Price: $518.47
4 Point Anchor for L-Series