Miniature electrical and magnetical probes are available from various manufacturers. The idea of finding a source of radiated emission with a "sharp edge probe" involves however a simplistic understanding of EM phenomena, I fear. It probably works at low frequencies where relevant device dimensions are far below wavelength. At least above a few 100 MHz, emissions are radiated by the distributed structures, e.g. a ground plane or case parts. The field maxima may be observed at other locations than the primary source.