The European Dead Zone map below will show you where to go.
The area marked in green is Maevic square and the area marked in blue is Trostland. Once you get a few in Maevic Sq. and you can’t find anymore just head back over to Trostland to respawn the enemies and the Dusklight Shards.
Here is a video that talks about the process in more detail and gives you a good idea on how to get them via the spawn method. If you know other ways to get them dont be shy leave a comment or link below!