I had a bit of a mishap and broke the roll arm on my P3P. While searching for replacements I came across this supplier - DJI Phantom 3 Pro, Advanced Gimbal repair replacement arms and kits - who has both printed ABS-like plastics and CNC machined aluminum parts. Both types are finished in silver paint to look exactly like the originals.
I bought the aluminum roll arm and did the repairs to my gimbal which I completed today. Wow, the roll arm is really a work of art! The image shows the new one on the left and the broken original on the right...