This mod replaces niko's standard outfit with tactical police uniform
install:
1.Drag all the files(EXCEPT "player_p.wdd" and "player_p.wtd") in GrandTheftAutoIV/pc/models/cdimages/playerped.rpf,
2.Drag "player_p.wdd" and "player_p.wtd" in GrandTheftAutoIV/pc/models/cdimages/pedprops.img,
you can use the latest OpenIV to open that .rpf & .img file.

Notice: You can also download "improved cop" mod from https://www.lcpdfr.com/downloads/gta4mods/character/2858-improved-cop/ to have a better game experience.