Broke our roof antenna - what now?

I backed our 2005 Prius out of the garage before the door was fully raised (oops) and the antenna ripped off. At first the antenna was dangling by a wire, but my dh ripped it off, and now we are left with the antenna base with one black wire hanging out...and really lousy radio reception. My question is - what is the cheapest way to get my reception back? I understand the whip antenna is supposed to screw out, but I think the whole threaded part is still inside the base so I can't just screw in a new one. Any thoughts?