I found these at Fry's Electronics for .79 in plastic as you see here. They also had them in aluminum for a couple of bucks but it weighed a lot more. I'm trying to keep the weight down so I went for plastic.
I never really finished the lower ring of the R5 head the way I had wanted it. I sanded it a lot back when working on it with an electric sander and 50 grit. But I can still see the spin rings in and it was bored and decided to take them out.You can see these spin rings on the left side of the photo. The right portion of the photo shows what happens when you use 120 grit on a mouse sander.
I slowly sanded them all out with 120 grit. Then put 240 grit on the mouse and gave it another pass. After that it was hand sanding going from 320, 400, 600 grit paper. I even went to 1600 grit but got tired of sanding and said let's just polish this with Mothers.
This is pretty close to how I want the silver ring to look. There are a few spots I needed to sand more with 600 and higher grits. Looks pretty good for just a few hours. When I get bored I'll pop the head off and put a few more hours in the spots I want to polish up better. I just use Mothers and a grinder with a buffing wheel I'm rigged up.
Right now the head weighs 19 pounds. You can still hear the motor groin when it spins. I need to somehow reduce weight. But where? I think one of the few things I could do is get rid of the upper plate that holds the pie panel pieces on. That might reduce 1 pound. But I'd end up adding servos and in the end adding more weight.