Eatso Fatso's Profile
Top Line has a good selection:
Also of course, the best place to sample some is Las Perlas on 6th downtown, across from Coles. They know what mezcal is all about. Most LA Bartenders have never heard of it.
If you find yourself wanting a good kick, try the NINETY-SIX Proof Mezcal by Metl, their site also can tell you where to buy it: http://metlmezcal.com