6-48 is the standard for Remington. Some were press-fit, but that's uncommon.
If you want a vintage silver or gold bead go here:
GunPartsCorp 6-48
If you want a hi-vis bead:
Truglo Fat Bead
I don't suspect new Remington is in a big to offer support for old Remington. They need to concentrate on keeping their doors open with their new lineup.