Where do you get the keyguards in Metal Gear Solid sons of liberty

Not sure what you mean by "keyguards". If you are referring to the key cards in Metal Gear Solid 2: Sons of Liberty that allow you to access certain areas in the game, one does not simply obtain them like a regular item. Increasing security level key cards will be given to you by NPCs (non-playable characters) during the cutscenes as you progress through the game. No matter what, you will eventually get all the key cards.