Got an '89 CE too, and after putting in the Sportline bars and Bilsteins struts, the car is begging for a manual transmission. This is my first automatic car in 30+ years of driving and I don't like it very much.
There is one thing that just might work, but have not been able to verify. It is my understanding that some of the 190E 2.6 cars have a manual. Since our 300CE has the M103 engine and the 190E 2.6 is also a M103, a swap might be pretty straight forward. I have my eye out for a trashed, junked manual 2.6 car so that I can get the trans and linkages out of.