If it were me I’d source an aftermarket pip and ask James here to colour-match some lume (in fact I’ve done just that in the past with an old Rolex that came with a replacement luminova pip.
As above what are my options for a replacement pip for a late 1960’s Tudor Sub? Would the pip from a more modern tritium insert fit?
Excuse the newbie question, how is the pip secured to the insert? Press fit, epoxy?