The only way to get a Mesmetron is to go to Paradise Falls, a giant shopping mall in Northeast Capital Wasteland.
Once there, talk to Grouse. If your karma is too high, he may ask that you bag up some slaves for him in order to enter. He gives you the Mesmetron and the list of people.
You can also kill Grouse and take the Mesmetron, but then you have to deal with the other guards outside the building. Killing Grouse will also prevent you from using the Mesmetron to enslave people for money.