I bought the Jazz Hot Stack Neck to go into my Carvin bass, unaware that the Carvin bass routing uses Bridge spacing on neck Jazz bass positions. Hence, it doesn't fit.
Re: Is it possible to get a Bass Jazz pickup cover from SD?
J Bass pickup covers are available from numerous spare parts suppliers, with or without polepiece holes, in both common lengths.
Attempting to fit a bridge/Treble position pickup cover over neck position pickup will result in a misalignment between the rod magnet polepieces and the holes through which they should protrude.