M16 Pull Pin Knob 2PCS Spring Adjustment Fitness Pop-up Knob Exercise Bike Replacement Parts for Fitness Equipment

Direct replacement: https://a.co/d/0iDZFXWn You could likely replace just the knob (you'd have to remove the current one with locking pliers) Knob: https://www.mcmaster.com/60205K71/ Threaded Pop pin assembly (potential replacement, might have looser tolerances): https://www.mcmaster.com/91712A556/ you'd have to use a thread checker gauge to confirm sizing.