This will add a standalone Military Cap to match the General's Colonial Duster by jdauley.
There is also a retexture of the NCR 1st Recon Beret - Standalone by Foedawg for download untill its confirmed the standalone work.

Installation: Click Download with NMM

Installation by hand: Extract the folders in the file to the main fallout 4 folder.

do these changes if you have problems with textures not showing up.

Fallout4Prefs.ini
[Launcher]
bEnableFileSelection=1

Fallout4Custom.ini
[Archive]
bInvalidateOlderFiles=1
sResourceDataDirsFinal=

to get the Beret open the console and type Help Beret 0 and then use the player.additem command to add the item to you inventory.

Hope you like it.