Go to http://mendingshed.com/kacoupling.html
The part is $5.95 and screws on with a left-hand thread. It is not "pressure fitted".
The easiest way to remove the coupling is to peel off the remaining rubber and expose the steel plate below. The plate has holes in it which can be used with a hammer and punch to tap it in a clockwise direction to unscrew it from the motor base.
Illustrated directions are on the Mending Shed web site. They were recommended by the Kitchen Aid service rep when I called.
Hope this helps.
Scut Farcas
July 2009