Oh that's way too expensive. Big Clive, I'm pretty sure it was him, showed how to build one a few years back on one of his videos. Pretty simple, a couple of trannys, an LED, some caps, resistors, and some wire. Worked, too, detected EM radiation

Cost maybe a buck to make, if you had no junk box of components. Hmm, if I can sell for that kind of price...