There's enough atmosphere to produce 1 bar of pressure at sea level, and I believe from playing Universe Sandbox, a .320 Gauss magnetic field on the Earth. Maybe some portion of that would be enough to really protect space travelers well. How much material would you need to equal the atmosphere and how much power/electricity would you need to produce a similar magnetic field for space travel?
As well as Earth at sea level would be 14.7 lbs per square inch of a low-Z material. (You don't need the magnetic field.) E.g. a 34-foot thick shield of plastic.