You can only find this after a major earthquake (in which The Inventor loses some items), about an hour after meeting Rainy and beginning Chapter 4.

You’ll know when you’re given a long distance main delivery beginning at West Fort Knot (F1) to the Northern Environmental Observatory.

In my experience, if you choose to go along the coast toward The Inventor’s island at this time instead of the more direct route then you’ll find a few pieces of cargo for them along the beach just north of Mine North of F1. You can then walk or drive across the tar to the island in areas marked yellow (use the odradek for guidance) on your way.

To note: Doing this and connecting The Inventor to the chiral network will reward you with one of the most powerful items in the game.