The Vault wasn't very helpful here, just saying that it can be found in "lockers" in the Big MT, but I haven't seen any. I need it to repair the Stealth Suit, which is broken. The Sink CIU is charging 15,000 caps to do it.

One suit of combat armor is in the X-8 kennels, but you a key from X-13 to get in and you need the field disruptor on your sonic emiter to get the key. The suit is in a locker above the kennels, so you have to go through the instatutional test to get it.