Thank you for your question, Big Ring! The set screw is not sold separately from the mounting anchor and a new one will need to be purchased. The correct part number needed will depend on the finish as seen in on page 2 of the Maintenance and Installation Manual below. Alternatively this screw may be found locally at plumbing supplier. It is a 8-32 x 8mm screw.
Best regards, Edward
Date published: 2019-08-15