Mopan Maya is a language that is still in use today in the southern portion of the Peten and parts of Belize. Most of the Mopanes also speak Q'ekchi because for 1000's of years they have interacted in trade with the highlanders of Alta Verapaz. There should be a dictionary of Mopan Maya (if not Maya to English then Maya to Spanish and vice verso) and if not you can speak to the Maya linguist Dr. Fidencio Briceno Chel or Dr. Otto Shulman. Dr. Briceno Chel did extensive field work on both Itza Maya and Mopan Maya and is the formost expert in Maya linguistics (in my opinion).