A collection of Military Grid Reference System (MGRS) data
Most of this data came from the National Geospatial Intelligence Agency http://earth-info.nga.mil/GandG/coordsys/grids/universal_grid_system.html#zzd1
The current MGRS grid zones are currently distributed from NGA as ESRI Sharp Files. This repo has the same files represented as KML as converted by GDAL
ogr2ogr -f "KML" OUTPUT.kml INPUT.shp