Someone just gave me their (used) Star D Tripod. It is missing a small white plastic ring that goes inside the tubing of one of the legs, on the 2nd joint, to enable it to lock into place at a particular height. (Without it, this particular leg goes up and down but does not lock into place.) I would like to replace this part rather than throw out the whole tripod. Can anyone point me towards Star D parts or something interchangeable? Thanks!