I was wondering how much power might be needed, thinking at first that it might be prohibitive, but it sounds entirely within reach:

"Last week's test was a success. We were able to completely fill the vacuum chamber with a magnetic bubble. The only thing that stopped the expansion was the presence of the chamber walls. In space this same experiment might create a mini-magnetosphere 15 km across."

Maintaining such a bubble in space would require about 1 kW of power and less than 1 kg per day of helium propellant for the plasma source. In return, the bubble would intercept about 600 kW of solar wind power.

(from the same NASA site.)

Very cool! Though the helium mass needed could add up for a long mission, at 1 kg/day. And, coming back from Mars, the solar wind would be pushing the wrong way, unless the craft could tack somehow... don't know what it would use as a keel.