Flight suits. Take away jippers and pockets from the ENT ones, dye the denim into departmental colours reflecting The Cage - Gold, Blue, Sandy Biege. Add a horizonal Starfleet (UESPA?) Delta and a Kelvin patch on each arm. In TOS whenever colonists or miners are shown, they're usually in jumpsuits. I'm thinking Devil in the Dark, This Side of Paradise... Perhaps the rest of the Federation get Stafleet cast-offs from previous decades.