Those are a pretty standard electrical item: several of the big electrical-minded companies make them: greenlee and ideal come to mind most quickly: the "slugbuster" is one specific model: it cuts the knocked-out slug in half, so it doesn't jam in the die like the original models would. There's lots of different cutters for these: all the standard electrical conduit and operator sizes, keyed holes, square and rectangular holes, DIN knockouts for computer parallel connectors, etc. etc. etc. If you really want to see them go, either put them on Greenlee's high-leverage puller or one of the hydraulic pullers (just about necessary for the bigger knockouts: they take a heck of a lot of force.)
