There isn't really "one" identity disc for any of the video warriors. There are the ones based on actual frisbees that they hold in their hands and throw around, and there are the foam ones that are attached to their backs with Velcro. I'm basing mine on the actual frisbee, and I'm using magnets so I can attach and detach it at will for a nice effect.
The frisbee - er, identity disc - appears smaller than normal, and according to this auction site, is a 9.25" diameter disc. So I got a vintage 1980 disc off eBay and went to work. Here it is so far:
I painted the disc with flat white enamel after priming. The central rings are printed onto a vinyl inkjet decal, and the outer ring is hand-painted. I am especially proud of the very trick magnet retention gizmo.