The Sennheiser SKP 100 G3 Plug-on Transmitter easily plugs onto microphones with XLR connections transforming them into world-class wireless units when combined with EM 100 G3 or EK 100 G3 receivers. This compact and lightweight transmitter has a run-time of up to 8 hours on just (2) AA batteries.
 
https://www.bhphotovideo.com/c/product/618848-REG/Sennheiser_SKP_100_G3_A_SKP_100_G3_Plug_on.html