All Grey Knights bits available are from new Warhammer 40k boxes.

The Grey Knights are the ultimate defender of the imperium against the manifestation of the warp, the only chapter of the second foundation, a descendant of the Holy Emperor. Dedicated to the destruction of all forms of heresy. With Bitz, of the Grey Knight, improve literally every of your marines.
Use Bitz squads of Purgators, Purificators or Interceptors and elite Grey Knight Terminator / Paladin and terrible Nemesis Dreadknight.