I've come to loath the ball-end ferrules. So many times I've serviced bikes with these levers and found the cable had cut a deep trench in the ferrule's tip, enlarging the hole while causing all kinds of frictional roughness.

The later AGC levers mentioned by Kontact forced the end of the lined housing to align with the cable, with the bend radius thus entirely within the lined housing, instead of at the restricted opening of a tilted ferrule meeting the cable at an angle (with metal on metal).

I have actually modified other ferrules to fit into both kinds of these levers, and I try to make the ferrule as supported as possible against tilting off axis with the hole in the lever housing. It's been a while, but I would start with a normal DiaCompe lever ferrule from an older traditional lever and shape with a file to fit as snugly/deeply as possible in the hole, perhaps reaming the hole as needed to give better support to the ferrule against tilting.
So that is my "Alternative Source for Dia Compe ferrules".

A swiveling ferrule is just a bad idea when the cable/housing is going to be forced off-axis with the exiting cable wire.