Replace stock Harmonic Balancer?

No single piece ones... the outer ring connected through the rubber ring is what makes the damper actually damp.

I suspect there are a lot of the PP dampers running OK out there. The issue is what gets damaged IF they fail. Other damper brands have problem from time to time.

The stock ones can be rebuilt as suggested earlier....it is all in the rubber used, and the care of installation of the ring to keep it centered.