This obsolete part is often lost during a needle assembly change out.  Its glossy blue paint job suggests it was originally supplied on nicer units when compared to the 46-8327 plain blue knob (below).   This rectangular shaped selector was found on BSR changers that were used in late model Zenith Micro-Touch 2g players in the 1970s.

This knob is obsolete but don't worry we are working on a solution.  Please jump on the waiting list to be notified upon its release coming in 2023.