I think it's the northern realms. If you structure it right it has good defences against all the other decks, and it has the potential seige assets to be utterly overwhelming
That's really bizarre. As far as I know it's something you start the game with. Maybe your save is glitched?
It should be in the crafting components tab. It's called Meteorite Silver Ingot, not Silver Meteorite, so you might have just missed it.
Try the herbalists that are in Beauclair. The one near the grandmaster craftsman and the Mettina gate, or one of the other few in the city. There's also one at Castel Ravello.
There's several herbalists in Toussaint that sell high level recipes and the white gull based ingredients (aether, hydrangeum, ect) needed to make them. From memory, there's one near the Mettina gate in Beauclair near the grandmaster craftsman.