Add a comfortable side handgrip to your camera rig with this SmallRig Wooden NATO-Rail Mini Side Handle + 1.9" NATO Rail Kit put together by B&H. The kit includes a wood-lined universal left/right side handle with a NATO rail clamp and a NATO rail that measures 1.9" in length to fit cages that do not natively have a NATO rail.
The NATO rail mounts onto your camera cage using the two included 1/4"-20 screws, and the handgrip clamps onto it, allowing you to slide it back and forth for balance. There are safety pins on the ends of the rail to prevent sliding off. The handle adds a shoe mount and a strap slot to your rig, and it can support rigs up to 7.7 lb.