Anyone interested in this should check out
http://www.protac.net. They quoted me one on for my Vulcan for $130. I think they are a small shop and would probably consider making one for the GZ. Main advantage is removablility. You could also look at
http://www.utpr.com/ for the Utopia back rests
If they aren't willing and if there's interest. We do metal fabrication where I work, mostly structural stuff. I could ask my shop manager how much it would cost to fabricate something similar. We don't have a CNC cutting machine so everything would be a straight cut shear and/or hand cut. In other words It wouldn't have all the pretty radius cuts shown on daddylaci drawings. We'd probably use 1/4" steel and not weld the bends. This means the bends would not be as sharp, but will cut the cost down significantly. The pieces would come as raw uncoated steel. We have no means of chrome plating. You would have to use a grinder to clean up any sharp edges and prime/paint as you see fit. Also you'd be on your own for all fastening hardware and the actual back rest cushion. Unless there is significant interest I personally don't see how we could make it cheap enuff to be worth it.