Easiest way to move (change pose) of a URDF robot in Gazebo

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I have a URDF robot that consists of some simple joints, links, and a camera sensor. I am spawning this robot in Gazebo using a ROS launch file and the sapwn_urdf node. Additionally, I have a TF publisher and robot_state_publisher as shown below.

<param name="robot_description"
       command="$(find xacro)/xacro --inorder '$(find myproject)/urdf/sensors/camera_box.urdf.xacro'
                robot_name:=$(arg camera_name)
                camera_name:=$(arg camera_name)
                base_x:=-1.0
                base_y:=2.0
                base_z:=3.0
<node name="spawn_urdf" pkg="gazebo_ros" type="spawn_model"
      args="-urdf -param robot_description -model $(arg camera_name)"
      respawn="false" output="screen" />

<!-- Provide transform between the parent and camera's world frame    -->
<node pkg="tf2_ros" type="static_transform_publisher" name="$(arg camera_name)_tf_broadcaster"
      args="0   0   0   0   0   0   $(arg parent_frame)   $(arg camera_base_frame)" />

<node name="robot_state_publisher"
      pkg="robot_state_publisher"
      type="robot_state_publisher"
        respawn="false" output="screen"/>

What I'd like to do is be able to move this robot (camera box) to arbitrary positions within Gazebo either from a command-line call or from a self-written node (C++ or Python). The robot could either "jump" instantaneously to another position, or move smoothly.

Is there an easy way to accomplish this? I can move non-robot models within gazebo (such as a piece of furniture) using a service call like:

rostopic pub -1 /gazebo/set_model_state gazebo_msgs/ModelState "model_name: 'chair'

But this doesn't move (or keep moved) the robot.

If I run the TF publisher node from the command-line, I can use it to move the robot within RViz, but it has no effect in Gazebo (as expected).

I assume that I could attach the "root" link of the camera-box robot to a non-fixed joint, attach a transmission, and move it this way. If this is the only way, that's fine. I was just wondering if there is a faster / easier and non-invasive way (especially during prototyping) to accomplish this.

Thanks for your help! Madeleine