Well velvet, you are in luck! We here are gamers just like you and we are glad to help!

I just so happen to have obtained both Excalibur from the Crystal and the Ribbon from Cerobi Steppe!

For Excalibur, You say you know how to get to XVI. That may be part of your problem. You do not need to go to XVI to get it but rather XIV. I just posted an answer to this a few days ago. Check out the third post in this thread click here.

As for the ribbon, this is not so easy... but it is obtainable. With some patience and lots of searching. Here is exactly how I did it.

From the save crystal at Journey's Rest in Cerobi Steppe, I reduced my party to one (Vaan) and equipped him with a diamond armlet, then saved. From there I headed North into the Crossfield. As you enter, there is a medium sized rock on your right and a small group of trees on the left. There is usually a Shield Wyrm standing in between, sometimes sleeping. To the right of the Shield Wyrm, you should see two single trees out in the open and a LARGE rock in the distance, next to the path. The treasure urn next to that large rock is the one that holds the ribbon.

Now, if you do not find the ribbon, go back to the save crystal at Journey's Rest - Save - Hit Pause - Quit to Title - Then Reload that Save and start again. The whole trip shouldn't take more than a few minutes from start to restart, if you avoid fighting and just head for the treasures. There are random treasure urns behind the medium rock and at the end of and around the group of trees (beware of the trap - you might want to cast float). Go ahead and get these treasures while you are there because they hold lots of gil and some nice items like weapons, ammo and misc. Then head over to the large rock by the path and check the urn there.

It may take you an hour or you may find it on your first try?! It is completely random, as far as I know. I know I collected over 100,000 gil, 2 Megalixirs, 2 Castellanos and 4 Fomalhauts before I finally got the ribbon. But, it comes in handy when I equip the Ensanguined Shield and frees up gambit slots for other uses!

Good luck finding it and please let me know when you do! If you need more help on Excalibur, give me a shout! We'll try to walk you through it!