I found this while snooping around in theater mode outside of Solitary. You need to perform the turret wall glitch to get into the room with the tanks, once you are in you can’t miss it. Here is what it looks like. If you notice it has the GRD helmet.
This is on my file share by the way. {fixed link}
> http://www.bungie.net/Stats/Reach/FileDetails.aspx?fid=24923266&player=Alphacoder308 <
youre a little late to the party bud, there are a bunch of youtube vids on how to find all 7 grd dolls that have been up for about a week