Shimano makes a top-pull cross specific FD (CX70) which would be my first choice. I used it for the first half of the season and front shifts were the best I've had on my cross bike (sorry, SRAM). More commonly, there is a pulley that is placed below the FD (the frame should have a place to screw it in), and this turns the cable around.
Any pictures of your cable routing through that Shimano top pull derailleur?
Don't have a picture of mine (sold that bike), but it looked just like any top-pull MTB setup. The cable left the housing up near the saddle at the last housing stop and runs directly to the derailleur.
There is also a german company called Speed that makes converters to turn a bottom pull derailleur to a top-pull. I'm using one on my sram FD and it works better than the pulley did.