I have had this Bialetti coffee maker for 2 years, now. I got is second (at least) hand, in New-Zealand, early in the trip.
I am attached to this coffee maker, for a number of reasons. So I will resume looking for a spankin’ new o-ring. Last time I tried, a few months ago, I wasn’t so successful. I almost purchased a whole set in the shop of a purveyor of Italian goods and delicacies in Roslindale. They didn’t have the 4-cup model. Otherwhise I’d have got it just for the ring.
Update:I found o-rings in France, I brought them with me, and I’m happy to report they fit perfectly. I think it’s neat.