on other cars, the shift cables are held on to the shifter and shift tower using a washer and cotter pin. as such, you can install solid bushings and they will function the same way, just with less slop. the Contour (and Fords in general it seems) dont use cotter pins, instead they use the rubber itself to hold the cable end on (i think its a horrible design personally). as the rubber gets old and heat cycled many times, it begins to harden and crack and this is what allows the slopping feeling, and even allows the cable ends to pop off the shift tower.
short of reworking the shift tower levers/pins there really isnt anything you can do other than just replace the cable ends with new ones.