These are often marketed for "testing" electronic shielding or, more nefariously, for trying to cheat slot machines or arcade games.
If you are an engineer or a researcher, you can buy professional EMP simulators. Companies like specialize in high-voltage pulse generators. can you buy an emp
Since you can't realistically buy a "doomsday" EMP, most people in the market shift their focus to . These are often marketed for "testing" electronic shielding