OK, so I finally found a little Hunt Specific guide to help with your question.
In order to find Fafnir you MUST do the following:
After speaking to Relj outside the Mt Bur-Omisace Temple, the Blizzard Strom will start in the Paramina Rift.
Now you MUST follow a specific route for the Blizzard to continue. The specific route is as follows:
- Freezing Gorge
- Head of the Silverflow
- Icebound Flow
- Karydine Glacier
- Silverflow's End
This, as I've already said, is the only way to make the Blizzard Storm continue. Fafnir will only appear inside a Blizzard Storm (I'm presuming that last bit though).
You should now be able to fight, and hopefully defeat, Fafnir.
As for the Ribbon question. I presume you must be able to end up buying them from somewhere at some point, I'll go have a look now though. If not, then there may be certain places you can find them as Treasure, or Steal/Poach them from an enemy. Give us about 10 minutes, tops, and I'll see what I can find. Jay Site Squad