OK, this is what we used to use in the steel mill. It is brutal and dangerous but very effective on anything up to a couple pounds in weight.
You need 2 steel plates, one large and one much smaller.
A piece of cardboard bigger than the large plate.
4 small non-conductive objects.
An ac line cord with a plug on one end and alligator clips attached to the black and white wires.
Peanut butter.
Place the cardboard in a suitable location and set the large plate on it. Place the 4 non-conductive items on the large plate and arrange them so that they will support the 4 corners of the small plate. Place the small plate in the middle of the large plate, resting on the 4 non-conductive items. Put a healthy dab of PB in the middle of the small plate. Finally, attach one of the alligator clips to the large plate and the other to the small plate. Plug in the power cord.
That's it. This will kill most vermin, but will also kill pets, children or you, so I hope you don't actually build it. I have seen this take down mice and large rats. Usually you can tell you got something because when the rodent shorts the 2 plates it will usually blow a fuse or trip a breaker.