I haven't found one like chevs and fords for our cars (if what you mean is one that just plugs into the wiring and crispens the shifts). what are you trying to get the trans to do? if you just want firmer shifts, the best you can do is to get a TransGo kit installed. if you want full control of your shifting, I don't beleive anything is available for the A604.

Does anyone know out there if that 3-speed neon trans has the ability for you to control your shifting? if so THAT may be an option. I know that the neon 3-speed is not computer controlled like ours.