I am not a modeler but by your description, you want something simple yet functional for still images.  You need to specify whether the loin cloth should be dynamic or conforming with pose handles to obtain the right, natural look of a flimsy garment.  This all depends on whether you use the Cloth Room for draping the outfit.  There are a good number of modelers in the forum, and I am sure they can create something for you rather quickly if you outline how you will use it in your workflow.