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On the wiki it says that they are lootable from a dragon, but where the hell would you find a dragon that can also be looted (as Saskia cannot be looted at all)?
The wiki has a few instances where it's wrong (some of the perks or abilities or whatever that are listed aren't obtainable, either), and I haven't heard of anyone ever getting dragon scales from Saskia. Even if they did, by that point the game is basically over and you wouldn't be able to use them to craft anything.

As far as I can tell, you can only get the dragon scales from Phillipa's house or from The Operator. Plenty of people have looked around the Temerian Quarter for the scales listed on the wiki, but I've yet to see anyone confirming that they found them.
You can loot dragon scales from Phillipa 's house in Loc Muinne, but only after you progress past a certain point in act 3 and her house becomes accessible. Path is of no importance. You can get it regardless. Plus, i think only in iorveth path, you can find 1 dragon scale in a chest somewhere down the sewers, but beyond than that, i do not remember details. Dragon Scale makes the Hard Difficulty Set Pants, or the sword Zerrikaternment.