Tankzone sells some 1/8 (close enough to the 1/9) scale 50 cal and M240 machine guns.  Stand by though they are pricy when shipped to the US.   I used their M240 on mine.   Internally, there was a guy who use to do an electronics upgrade for it.   He quit doing them, I all but begged but no joy.   There may be a way of using ElMod electronics in it. Phil and I at one time talked about it.  ElMod can handle up to 12 volts. You would have to use a custom made NMh battery in it.  Other than that, there is really no one that I know of.