This is a pain in the bum really.
The four weapons are easy to loot from enemies or buy from several vendors. The clothes and helm, however, are an nightmare.
Thankfully I found a location with pre-deceased people that had clothing on them. The labs at Edgewater that require you to turn off the electric gates and fight an array of robotic enemies, have dead scientists all over the place. There was two there that had the loot required. Also found them inside.
Scylla's Abandoned mine also had uniforms lying about.
The loot system is random so early on Edgewaters vendors sell miners gear you can buy dirt cheap. They seem to disappear later on in the story though, especially after the deserters return to the town.
Areas to rule out looking are Groundbreaker and Monarch. I never seem to find any there. But randomly come across them on Terra-2 and Scylla alot.