Concrete....Lots of concrete...
Pah! We shouldn't go down the high tech route, after all, NASA isn't with it's revamped Apollo 'cram a few guys on top of a big firework' approach, and do we need to mention good ol' Soyuz? There's an easy answer to the shielding question.
Concrete! Yes, folks, good old concrete. We build a big ass, several metres thick concrete shield around our brave explorers space craft, clad it in lead for good measure and launch it at Mars. It doesn't need power like a new fangled shield (though bigger engines might be useful), and the materials are simple. Given the current crisis in the building sector, we even have adequate numbers of desperate construction workers to build it.
Build the shield big enough, you could even look at Nuclear propulsion (on the opposite side to the crew, of course)......