Best thing you can do is equip the Hoarder mod, then go kill those girls in the driller cars. Just keep walking in-and-out of the room to make it respawn. They should drop a Tungsten after almost every death. Once the baddy stops respawning, just press the Back button on the controller, enter the Mission Information menu, press Y, answer "No," then answer "Yes." This will leave the mission, but you will keep the items you picked up during the mission.

You are guaranteed to get a tungsten(Along with a track plate) in military city in the bottom-most area of the sewer. Roll under the flamethrower guys and break the three crates for free stuff.

There's even a Polymer on the far right of the second map, and a sulfuric acid on the far right of the sewer. Lots of goodies to be found on the military city map.

And equip lucky penny and hoarder

Is that the only place to find them (especially Track Plates)?