OK in order to get the riot security suit, and the elite Vintage suit you have to finish the game on any difficulty to be able to get their schematics. But the security suit you cant collect the schematic on your first playthrough of the game! Lets continue, Shall we?
Riot Security suit-
In order to unlock the riot security suit, you must finish the game on any difficulty and it will be in the stores for free! WOW! It gives: 25 inventory slots and 25% armor! It gives a lot but so far almost all of the suits will have that.
Elite Vintage Suit-
The schematic for the Elite Vintage suit is on chapter 6 where you meet Ellie , Y'all meet up and get attacked by necromorphs, You however will be attacked by a brute :P after you kill it go to the statue of the vintage suit and there should be a schematic for the Elite Vintage suit! it gives 25 inventory slots and 25% armor!
The Security suit is located in the security office storeroom. To enter the office, you'll need to statis the slamming doors It is in chapter 4. It gives you:15 inventory slots and 10% armor!