I don't think they do rat-sized ones, but I have a couple of electric mouse traps, the mouse goes inside (it can't get back out as it has baffles in there), as soon as it steps on the metal bit to get the bait, pfzzzzz, mouse is dead, and triggers a red flashing light to let you know the deed has been done. Pick up with a carrier bag, invert trap and flip the lid open, the corpse will drop into the bag. knot the bag, put it in another bag, and it can go into household waste.
I have to do this, my husband is too big a wuss to do it. I don't like the ordinary spring traps, if they don't snap over the mouse's head, they can get a leg and then it's a slow death - unless you draw the short straw and use a housebrick to put it out of it's misery (speaking from horrible experience there). Yes, they are pricey, but well worth it as they're humane, clean and can be used with dogs and kids (I have both, and from time to time a mouse problem as I live in a house that's near a farm, the farmer is none to fastidious in his habits (that's a long story that involves environmental health, a pig ban and a chap that lives in the village that does aerial photography for a living!!)
I suppose you can always google electric rat traps to see if they exist, otherwise I'd use the specially designed pre-baited rat boxes, they're sealed so dogs and kids can't get at them. Was told by the Rentokil man that mice and rats won't share a house, so I suppose I get the lesser of two evils. I'm sure the farmer at the back has rats and worse.