One can be found at X-7a "Left Field" artillery launch on the corpse of the unique sentry bot, RY-589 Ultimo bot.
Another one is in the Forbidden Zone dome, in the second floor room, just left of the brain tank.
One can be found on top of the X-13 research facility. In order to reach it, the player character must jump down from the cliff to the north. The cliff can be climbed by jumping up a pile of rocks just to the west of the Big MT west tunnel.
The last one, along with various energy weapon ammunition, is in the same room as above in a chamber connected to the exit platform. It is on a table in the middle of the room, and it is in good condition. This one requires a force field to be disabled in order to gain access to it.
Behind the scenes
The LAER uses the same electric beam weapons technology also developed in the Secret Vault.
It was at first a cut energy weapon of Fallout: New Vegas, appearing in the concept art section of the Fallout: New Vegas Official Game Guide Collector's edition complete with its own icon in the game file.
The name implies a function like modern attempts at making electrolasers which use lasers to create a conductive plasma conduit in the air and then discharge an electrical differential across the conduit. While practical devices do not yet exist, the concept has been proven and the effect on the target is dependent upon the amount of energy delivered. At lower powers the effect would be much like a stun gun and higher energies being more like a bolt of lightning.
A Brain's Best Friend ·All My Friends Have Off Switches ·Coming Out of Her Shell ·Field Research ·He Came... And Went ·Influencing People ·Midnight Science Fiction Feature! ·Old World Blues ·Picking Your Brains ·Project X-13 ·Sonic Emitter Upgrade ·Welcome to the Big Empty ·X-13: Attack of the Infiltrator! ·X-2: Strange Transmissions! ·X-8: High School Horror! ·X-8 Data Retrieval Test
Cardiac Arrest! ·Make up Your Mind ·Making Friends ·Outsmarted ·Spinal-Tapped
Automaton ·Cardiac Arrest! ·Caza-Death Dealer ·Dog Run I/II/III ·Evil Genius ·Klein Destine ·Mad Scientist ·Make up Your Mind ·Making Friends ·Mobius Strip ·MT Space ·Outer Space ·Outsmarted ·Spinal-Tapped ·VR the Champions I/II/III
Big MT ·Big MT north tunnel ·Big MT east tunnel ·Big MT west tunnel ·Construction site ·Elijah's Watch ·Forbidden Zone dome entrance ·Hazmat testing ground ·Higgs Village ·Little Yangtze ·Loading station ·Magnetohydraulics complex ·Mysterious cave ·Saturnite alloy research facility ·Securitron de-construction plant ·Signal Hills transmitter ·The Cuckoo's Nest ·The Sink ·The Think Tank ·Waste disintegration platform ·X-2 transmitter antenna array ·X-7a "Left Field" artillery launch ·X-7b "Boom Town" target zone ·X-8 research center ·X-12 research center ·X-13 research facility ·X-17 meteorological station ·X-22 botanical garden ·X-66 Hexcrete archipelago ·Y-0 research center ·Y-17 medical facility ·Z-9 Crotalus DNA preservation lab ·Z-14 Pepsinae DNA splicing lab ·Z-38 lightwave dynamics research ·Z-43 innovative toxins plant ·Ulysses' Point