I have the aluminum housing from a 72" Aqua Medic metal halide setup. It should be easy to cut to your size and has everything (spacer pieces and end caps) except the wiring and lights in it. No fans in it. I will have to dig it out for more info/pics.
I also have a Current PC setup that has been gutted. 48" long. May be able to trim it down as well. Has fans included in housing.