The cream sheep-fleece hooded one-piece can read as a disguise. It is not. The night crew found it in their spare-kit bin when Chima started working nights, two sizes too big, with a small brass bell on a cord at the throat.
Keeping the fleece and bell as workwear keeps the class detail in the story. He is a teenager with a shift, a locker, and a supervisor — not a fable creature in fancy dress.
The bell rings when he crosses the warehouse floor; nobody has to look up to know he is coming.