Never heard of those failing either, on any boat. On our 40 Ocean, they're much stronger than the deck rigging. And yes, they're something a (rod) rigger can manufacture, possible with help from a lathe workshop (one end has a thread cut into the rod, which isn't standard with rod rigging).
I did hear of the bolts tying the outer and inner chainplates through the deck together, and replaced them after I discovered a small crack in one of ours. The chainplates are also prone to leakage and crevice corrosion if not rebedded since they were new and can fail if not taken care of, which happened to one owner of a 38 Ocean we've met.