If I am understanding what you want correctly, you're after a transceiver unit with dual receivers and a single transmitter in a single unit. Something along the lines of the Yaesu FTM-400, or the Kenwood that SCWolverine mentioned, etc.. Other than those types of rigs, you'll have a single receiver and transmitter, which precludes actually listening to more than one frequency at a time.
Instead, they(most anyway) will have a "dual watch" or similarly named feature which will rapidly change the receive frequency between the "main" and a "sub". If the "main" is inactive, and a signal is detected on the "sub", it will typically remain on the sub for some specific time period(sometimes there are several preset options to choose from), or until no signal has been detected for "x" amount of time, then it will switch back to the "main".
There really isn't much advantage to having a dual receiver rig, and in some cases it can become very confusing, very quickly. Mine(Yaesu FTM-400) is almost always set to the most used of the local repeater frequencies. In inclement weather when Skywarn activates spotters, all official traffic is on one repeater and any other traffic is asked to use one of the others. When things get exciting it's all too easy to have the wrong frequency selected and give a report or interrupt with non essential communication. Just some things to think about.
