Ask these guys: http://www.fmtunerinfo.com/index.html
Generally speaking though, a very sensitive tuner is going to be found in a component tuner or a receiver. Portables not so much. A loud, high quality vintage boombox will probably cost you more than a decent receiver. To really suck in those college stations your best bet is a receiver with a serious tuner section (fmtunerinfo has <a rel="nofollow" href="http://www.amazon.com/Winegard-HD-6010-HD-Radio-Antenna/dp/B001HKM1HM/ref=sr_1_6?tag=comments-r-20">a list</a>) and a good FM antenna connected with high-quality coax.
I resorted to building my own half wave dipole, which is now hooked up to a Yamaha CR-600 through a decent 300 ohm balun. This setup allows my valley-living ass to hear KALX's puny 500-watt signal from 30 miles away.