Nurgle drones are the double-rotor creations with a small body, right?
Depending on how many you're after, I'd probably try and convert them- the basic shapes are pretty simple.
I don't know about the scale, but space marine jump pack engine exhausts may work for rotors, and a Tau Fire Warrior head sort-of suits the body? There are probably better pieces out there- that's just what immediately came to mind.