[PStamler]

It sound like your problem is not RFI (Radio Frequency Interference) but EMI (Electro-Magnetic Interference) Another mic with a hum-bucking coil is the Electro-Voice RE15/RE16 (same basic capsule, but the 16 has a pop filter and a slightly brighter sound). But small transformerless condensers (like Oktava MK012s) will ignore the noise too -- why exactly do you prefer to use dynamics in this situation?

Peace,
Paul Stamler