That's odd, it should have been added to the synthesis menu after finding 70 lucky emblems.
Have you synthesized all items currently available on the moogle shop menu? Did you complete the materials collection and photo missions to unlock more items?
I'm not 100% sure, but If remember well not all items are available immediately, but after synthesizing a number of items a new batch gets added to the menu.
Try to unlock and synthetize any item that you haven't already (if there's any) and see if that triggers the royal ribbon appearing.
I hope this helps... If not, maybe the game is bugged.