Larry mentioned a Fluidamper. It has no viscoelastic rubber to fail.
While I've never personally exerienced a failure of a Fluidamper Balancer - I know of one Dyno shop that would not allow any Fluidamper equipped engines on their dyno. Evidently there had been at least two failures there. I changed out the Fluidamper for a TCI balancer on my GT40 engine when I dynoed it there.
Do they make a Fluidamper with integral pulley?