Drivers: Racecar drivers can wear any of the NASCAR or top speed choices.  

Boat captains: You've got choices here—be a cheeky pirate, wear a captain's or fisherman's costume, or choose a sailor costume. 

Astronauts: this one is super clear - there's a relatively large selection for these. 

Conductors: there are a couple of train engineer costumes, or wear a dark suit or coveralls/an industrial bib and grab a conductor's hat.