Once the rivet holes get loose, there's virtually no fix other than replacing the damper. I'm not even sure if the shops that specialize in rebuilding them can rehab one with that kind of wear. Rebuilders are very fond of their work- - - -bring lots of cash! What width belt are you running?

I'd suggest putting an ad in the "parts wanted" section. Somebody here probably has the part you need or can be of assistance in finding one. I build up a new 2-groove balancer with the narrow belt with readily available over the counter parts, but it requires a little machine work on the hub to make the belts align properly. Even considering the machining, the cost is a lot less than the balancer rebuilders want for their services.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!