I mean, you can build one yourself, but a real damaging version would require a lot of power.

Unfortunately due to the inverse square law, they don't have a very long range.

I guess a phased array emp would be the best way to do it.

Not easily done with the DIY hacky way of doing it with a coil and teaser generator, but I'm sure with some decent mosfets and transformers, it should be possible.