Tell you whats amazing. My GZ had better light output than the Shadow Spirit i have now. I wish my shadow had as good a lighting as the GZ, i cant see crap at night lol.
There IS a place that sells lightbars for the GZ...
Universal light bar -
http://www.classiccruiser.com/product.asp?item=379600
Spotlight - just type spotlight in the search box and you'll get a ton of them listed.
You could also try ebay for some smaller type motorcycle driving lights that they use on sport bikes. I was thinking about modifying something to get them mounted somewhere on the GZ i had. I wouldnt recommend putting lights on engine guards, the vibration might be too much (just a guess), not to mention having wires across the bar, frame and into the headlight area.
I'd also recommend looking on ebay for xenon bulbs for the headlight. They make a big difference as i had them on my bronco and i know i seen them for motorcycles as well.