Bottom of the conveyor belt by the train station office. Another may be found in the second to last building (head due south) inside Boulder City Ruins. First floor, bottom of the stairs behind the chair.
To the southeast, down in a radioactive puddle with part of a bus, a burnt out car and large stack of radioactive barrels (+2-3 rads per second throughout most of the area with little to no protection). Follow the road south past the camp to the first billboard on the left (corvega billboard, the back of it will be facing the player), turn left into a small ditch that leads right into the puddle.
The image is a flipped and recolored version of the front cover of Adventure Comics 428, by DC comics. It is the origin issue of the character Black Orchid; this character was a master of disguise and imitation, hence the link.
¡La Fantoma! translates as The Phantom!, which lends verisimilitude to the idea that the magazine would give the reader ideas about how to sneak more effectively.
The exclamation mark style points to the idea that this would be a Spanish phrase. La Fantoma, although sounding Hispanic, under closer inspection the phrase actually only translates to the desired phrase The Phantom! (as an outcome of direct translation) from Romanian - this makes the first exclamation mark redundant. In Spanish, it would actually be ¡La Fantasma!.