My first thought was to make an sdf file with two links (one for the cube, and a plane with my material applied) with a fixed joint between the two. The cube link has an inertial element, and a collision element, while the marker is only visual. This produces the correct visual, but I found that it breaks gazebo and subtle ways. For instance, I cannot interactively translate or rotate this model in gazebo. I cannot use the builtin model editor either.