Those are definitely by Lorraine Schwartz. Try calling Bergdorf goodman, or calling the lorraine schwartz store they might be able to help. None of Lorraine's pieces are sold online anywhere.
good alternative thanks for the tipIf LS is too costly for your blood- google Melody Eshani, she has a very similar style of earring. I think they cost about $50 and in a few choice of colors.
Her fans send in pics of themselves wearing her stuff- her is a pic of the geometric earrings, just like Rhianna's pair in the photo.