Nearly any of the newer digital models would do what you need.
Here's a good site to help decide what to look at next!
http://beaconreviews.com/transceivers/Specifications.asp
The ones you'll hear the best reviews on are the Orto S1 (Got one, love it), pieps DSP, barryvox pulse, Bca tracker II. Those are all great units, the tracker is likely the easiest for single burials but much more difficult for multiples, the rest seem about the same to me, I just like the way the S1 works, but it's expensive.
The M2 is pretty old tech & yes, has been discontinued. If you can justify it $$ wise, you'll be doing your fellow riders a favor by picking up a newer, easier to use unit.