I completed the contract of the Nekkers and Louise Merse rewarded me with a diagram of a high-quality Silver Sword, I have all the materials to make it except the silver ore. Where can I find it? I've checked all the merchants and none of them sell silver ore.

PS: I'm in Floatsam.

There is a dwarf somewhere in the flotsam of the street where he is a blacksmith and sells silver ore. You'll also find silver ore in the quest outside the flotsam in the northern cave (remember the quest name was Marina).

Just finished the game and I loved it. I haven't played Witcher 1, but after playing Witcher 2, I suspect I may in the future. I also wish I could run Witcher 3 on my laptop lol. The game was a little short for me, but other than that I thoroughly enjoyed every part of this game.