EDIT - AHHH, you said diamond one. No, when I shopped for the trinity I never saw one in diamonds, in the ultra thin. Customer service at Cartier is EXCELLENT! Maybe give them a call and ask!
I just sold one like to a fellow PSer. When trying to decide an asking price, I could not find it on the Cartier website anymore....I think it has been retired. I absolutely loved it! But I needed the finds for another project my heart desires more now.....darn PS!LOL
As far as I know they only have diamonds on their medium and XL Trinity rings, you will find all their designs on their website (I think the link has already been posted above).