I modeled this on request from a relative who has constructed a scale model of Thomas the Train Engine for his grandchild. I still need to smooth out the bridge of the nose a bit (nothing a little sandpaper couldn't fix). The model is currently 6 inches in diameter but could certainly be scaled up or down. Enjoy!

Solidworks file was created in Solidworks 2014.

7 year edit:

I have added an STL with the pupils removed and thickened the face (added 0.5in)