I use a "four paws" harness for my dragons. It's simple, doesn't bind their spikes, and they don't seem to mind it as much as some of the other types out there. Four paws makes them for iguanas, cats, small dogs, even ferrets and rabbits. They're all the same thing, just packaged differently. If you look for the ones packaged for the different animals, you can choose colors, since the iguana one is only in black. I've ended up with red, green, blue, purple, pink, and black for my dragons.
Are they like a "one size fits all" kind of thing? or what?