Hi,
Friends of mine went to Mr. Patrick Glynn on middle abbey street in dublin's city centre when getting an engagement ring. he is a jewellery designer and manuffacuter. he is on the right hand side near a newsagents as you walk up the street from O'connell street. he has a white sign sticking out from the wall with black writing on it. they were very happy with his service.
Hope this helps,
Muzzy.