This mod added CIA coat and earpiece to niko. Some guys have already made a CIA coat model for Louis and Johnny, but for Niko as a cold killer who really worked for the agency(ULP) for a while, I guess the suit may also fit well.
install:
Drag all the files in GrandTheftAutoIV/pc/models/cdimages/playerped.rpf.You can use the latest OpenIV to open .rpf file.

NOTICE: all the clothes in this mod are ADDON, which means you will need to use a Native Trainer to spawn that outfit.