You could buy an antenna amplifier, might be better off just getting a better antenna. Is this outdoors? Terk makes a lot of indoor antennas, not sure how well they work. Check Amazon for antennas, a lot will depend on how/where you're going to mount it. Automotive antennas are generally designed to operate with a metal ground plane, like the sheet metal in the vehicle. I used to live in a very poor reception area, I had one like this:
Now I generally make my own antennas. I can customize them to the location where I'm putting them so they're less obtrusive. Just keep in mind that smaller antennas are always a compromise, comparing apples to apples, size does matter for antennas. Hope this helps.