You can find them in Ur...often same street or one or two away from the locked area (wiki will tell you locations). If you are in the abandoned apartments, they will be located on floors in the building.
You can get them from the dust traps in the Ancestral Lands.
Look nearby for keys. Often, they will be behind a pillar, bush, or rise in terrain. Sometime they're on a nearby street. Some keys respawn in a minute or two, some in 10 minutes. If worst comes to worst, you can check in the Glitch Wiki under Keys.
Look closely for the small glow. Walk back and forth a bit so you can see behind rocks and other things that stick up from the ground (same goes for guano).