Only hard top swivels for illuminated visors are or at least were available. Gm has them or had them but they were not cheap. $55? Eric will post & correct me in a matter of minutes
If you can grab the peg on the swivel & move it. It is not the bushing going bad. On a t-top illuminated visor or Hard top we put a small weld in it to prevent the peg itself from rotating.
Well, I had replaced my visors several years back--due to bad/ saggy covering & don't remember original illum'd visor doing the unintended swivel thing. So, I'll hopefully find my old visors in the "shed" & just switch/ transfer the "new" visor/ mirror portion to old swivel... Wallah (I hope)!