3Dconnexion SpaceNavigator USB (3DX-700028).  Used, in excellent condition.  8 units available.

Key Features
  • For 3D Navigation in CAD Applications
  • 6-Degrees-of-Freedom (6DoF) Sensor
  • Manipulate Content & Camera Positions
  • Push/Pull/Twist/Tilt the Controller Cap
  • Pan/Zoom/Rotate 3D Drawings
  • Compact Footprint
  • Two Buttons
  • Windows & Mac Compatible