Im currently working on my version of the mediachance spinning dof-machine, and I have grinded a blank CD with a very fine sandpaper. However, I'm not really satisfied with the results, so I was wondering if any of you knew a better gg for use in a spinning adapter?

Window foil. I got that tip some time ago. It is very bright so you'd have minimum light loss.

you may want to ask Redrock or some other companys if they sell GG's separately

Yes, perhaps I'll do that. I'm not quite finished testing it yet, though, so I have to see if it's worth spending more money on.