It is received from Christine as part of her dialogue: several Perception and Intelligence checks are necessary, along with polite responses. To get the proper line of dialogue you need to ask her if she knows what the machines around the Villa are for. A dialogue option to acquire this perk has a Perception check of 6 followed by an Intelligence check of 6.
It is of limited use in the Sierra Madre proper due to the shortage of fission batteries.
Though this perk seems worthless after the add-on is complete, the vending machine in Elijah's room in the abandoned Brotherhood of Steel bunker, allows for the purchase of any items unlocked on the vending machines at the Sierra Madre. It can be noted that some potentially difficult to obtain items, such as weapon repair kits can be bought from this vending machine (provided they were unlocked during Dead Money), with Sierra Madre chips - making this perk much more cost effective than crafting weapon repair kits at a workbench.
