I was turning one of Neil Scobie's Offset Turned Doughnuts, American Woodturner, February 2014, with a Penn State Sorby revolving stub center knock-off in the tailstock.  The center cracked just before the internal bearing. I'm OK, but that is sort of a scary situation.

Went shopping for a replacement today. The Sorby's are pretty expensive, about $89. And, yes, I'm sure they are very good. But most of the online stores appear to be out of stock.

Went to, The Woodturning Store, to check their price. They don't carry them, but they do carry a similar product from Axminster. I have several Axminster chucks and find them very well made and solid. The price on this was $54.99. Don't have it yet, can't give it a review, but I suspect if it is built like their chucks, it will last a LONG time. They have 2 sizes, one about 7/8" in diameter, the other 5/8".