Looks to be a repro of the original ring.... and seems to be no longer available. I found some on HBC and Muscle Car Central websites, but none to be had. It could be oem, but with no identification, I'd guess repro first. All the available aftermarket rings have the continuous ring of teeth and don't fit or stay on well, as you already know.
I did a search for NOS but came up blank. Your best option is to ask for one on here. I'm always amazed at what comes out of the woodshed for parts...
