Is there a model for the Sphero robot from Orbotix, or something close?

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Hi, im trying to model a Sphero but im having some trouble because im new with ROS and GAZEBO, and i cant really a mobile spherical robot, in a stable way. I using ROS Jade, with Gazebo 6, and i was wonder if there is someone who could give some advice on how to do this.

I tried a sphere with 2 parallel wheels inside with no collisions, but all i got was a ball going forward and backward, then i tried to use one more wheel vertical to try to spin the sphere into changing direction but since this wheel follow the Sphere's body, i think its easy to understand that it doesn't work. I have search for Sphero models but i cant find anything. Any help would be appreciated.

Thank you for your attention, Ricardo Martins