@VinceS

The *.exe files are just self-extracting ZIP archives. They can also be extracted by WinZip, WinRAR or similar tools.
After extraction you will find the map file "gmapprom.img" in the "MapData" sub directory. You can rename "gmapprom.img" to "gmapsupp.img" or "gmapsup2.img" if that's suitable for a 276c.