Is that the only frequency you're concerned about? Is it close by, with good signal? Is it a repeater broadcast?
Anything is better than stock, unless it's a local trunked system with good signal. It doesn't appear to be your case.
First of all, you will need a SMA-BNC adapter unless you can find another/better antenna with the SMA connection on it. Aside from that, and aside from getting a mobile antenna to sit outside your window or something I recommend either the radio shack 800 model or the Diamond RH77CA (that is the BNC model) I believe they also offer a SMA model. If you still decide to go with a portable type you should probably also get a connector that pivots/right angle adapter. Otherwise it's going to stick straight out from the unit, horizontally, which will possibly degrade it's ability/defeat the purpose.