There is no uniform to put on

Half a day lost to an assumption. NCPD officers walk around Night City in uniform, so there must be a uniform to equip. There isn't.

What those NPCs wear is a character appearance: a complete, pre-baked version of the whole character, stored inside an archive (one of the game's data packages) and selected by its appearance name. It is not an inventory item. It has no TweakDB record, no entry in the game's database of items, that you could hand to the player, and there is no item ID because there is no item. I searched the script dump for one far longer than I should have, assuming that anything I can see in game must have a handle I can reach.

That left two ways out. Build a custom appearance for V, which means archive work, two body types, and a maintenance bill every time CDPR patches the game. Or find real clothing already in the game that reads as NCPD at a glance.

I took the second. Five vanilla items, straight from the base game: Cop_01_Set_Jacket, Cop_01_Set_Pants, Cop_01_Set_Boots, Cop_01_Set_Glasses and Helmet_02_basic_01. All five exist, all five equip the normal way, all five survive a save and reload, and none of them means touching an archive.

It isn't the exact NPC uniform, and I've stopped pretending it has to be. At pursuit distance, in the rain, nobody can tell, and the silhouette is right. The lesson is the cheap one: seeing something in game doesn't mean the game lets you reach it.