Wider tires will stop the meandering, but you'll have to replace the stock wheels to mount a wider tire. Some people have used stock rear wheels (bought from a dealer) to mount wider tires, 175/55-15, the same tire used on the rears. The wider tires on the front will cost you about 2 MPG though.
As a veteran driver of small cars, here's how I deal with it. I pull my left foot towards the seat until my knee touches the steering wheel. Bolstered this way, I can zip right past big trucks without getting blown around in the lane. It also helps with the meandering in sections of CA freeway with rain grooves and when there are high Santa Ana winds.
Hope this helps...