sensor unit, firing unit.. where to find them?

[steelgod101a]

ok, im on the second to last mission. Gotta build this trap that requires sensor units. Also id love to make this little shotgun that seems to require a firing unit. Any idea where these items are located? I've been every where, done just about all there is to do.. minus the multiplayer stuff, and have not come accross these items.

[OtterlySwift]

If you have been to the singularity area 3, you can teleport to the location closest to that singularity and loot up the entire complex and you will come out with a decent amount of sensor units and firing units. Another way is to do Normal/hard mode co-op missions. I get a lot from going back to that place to loot them and then farm the rest from co-op missions and hope I get some at the end.

[steelgod101a]

thath may be why i never found em. I stoped looting everything accept the special item boxes for blueprints once I figured out how to get unlimited inventory. lol