These characters are explorers and adventurers, so versatility in their attire is key. They won't know what their exciting day brings them while on the job, so tactical field wear is optimal. Also, some adventurers have villains after them while on missions and expeditions, so a few weapons and/or whips won't hurt. 
Adventurers should opt for an Indiana Jones-inspired look with the fedora, whip, and attitude. 

Tomb Raiders should go for the huntress or huntsman-inspired costumes, the black widow, or another catsuit, and you'll also need some weapons to fight your villains.

Anthropology or Archaeology professors can opt for paleontologists or safari/zookeeper costumes with a safari or fedora. Consider Indiana Jones, who is on break at the university teaching classes and spending time analyzing his findings in his (or her) lab. 

Zookeepers: Anything khaki that looks like a uniform is perfect. Feel free to dress up as the animal of your choice—you'll get a ton of laughs!

Hunters can wear any of the above, Jane the Hunter, or other hunter costumes.