Common: (You just have to play the game)
Any Beast lord cape works well for Chosens. Lore wise Chosens wear trophies of their defeated foes and that could include their skin. Using the Skaven cloak fits with most styles since the cloak resembles a Plague monk or Warp priest and those 2 types of Skavens are pretty powerful so its a worthy trophy to wear draped around your shoulders. That or you could wear a cape that looks like you just hunted a fancy deer.
The devs didnt remove the marauder body armor for chosens from the game they just removed it from the loot tables. the devs did that because they dont want careers having so many armor appearances of other careers. That armor you are talking about originally dropped off of Praag PQ bags. Now that the Devs added an option to only see the enemies real armor maybe they will bring back more cross career appearances.