Update:
Yesterday, due to the sterling efforts of Simon Burford at Elite Optical, I received not only a free replacement eyecup for my HIKMicro Lynx thermal monocular, but also a complimentary screw-in neck lanyard to fit the device. This was an unsolicited gift courtesy of Mr. Burford.
I regard this as exemplary customer service, particularly considering the fact that the firm from whom I actually bought the monocular, and HIKMicro themselves, couldn't seem to care less about my problem.
I recommend Elite Optical to all my fellow forum members. (I have no connection with them other than as a satisfied customer.)
Thank you, Mr. Burford.
maximus otter