The MFC Grenades and MFC Grenade Clusters added with GRA have their own textures.  However, these textures are duplicates for those found in the base game.  I have altered the meshes to point to base MFC textures so that texture replacers for MFC will now also properly retexture grenade variants.

Comparison image is using Christopher Wallace MFC retexture.
THIS DOES NOT CONTAIN TEXTURES.  YOU NEED TO DOWNLOAD THEM YOURSELF.  I recommend downloading here: Laser Rifle Hi-Res Retexture