FWIW a Friend of my family has a stainless roll up tonneau, It looks good, it's lockable, easily retractable and it can support over 500lbs on top of it when its out. I can try to find out where he got it from, IIRC he paid around 700 for it.
EDIT: It was something like this one. http://www.pace-edwards.com/Full-Metal-JackRabbit