Kind of odd, I thought Kung and kings were pretty well identical in the battery compartment? I could have sworn others confirmed the 70mm buttons fit? I know they fit in my SR king.
Well you can use any manner of unprotected batteries, I’d recommend NCR18650B unprotected button top, or flat top and you’ll need to add a button. High quality cell and you’ll get some serious runtime with 4x 3400mAh.
I use simple laptop pulls with brass nuts soldered on the pos end.