Back in "the day" they used to rig up a pully/cable system. The wheel ebd had a drum on the end, with cable wrapped around it. From that the two ends of the cable came out, one to port, one to starbord, to pulleys. Then they went back to each end of the transom, to two more pullys, then crnter to meat at the motor. So as you turned the wheel, it would pull one side of the cable, wile letting the other lose. The best setup? No not realy, but cheap in you can find the parts from a scrap boat.
Now as Greg is saying, there are steering systems out there. If I am not mastaken, some are pretty cheap also. I don;t know if they have them in your aera, but West mearine has some good deals, and a real nice catalog.