I don't know if this helps any but, I was going to use a metal halide lighting system but I didn't. I went to Lowes and Home Depot to look for the metal halides and found a couple. Like you said, you DO need to get a fixture but, all I could find were huge outdoor light fixtures.
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can i use a standard fixture?
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No. There was standard size and oversized bulbs for metal halides. The standard sizes were 175W and I actually bought two of those, thinking they would work in a regular incandescent outlet - I was wrong, they didn't. The bulbs that I bought said on the front of the box: Do not use in a standard incandescent outlet. I didn't pay much attention to the box until I was already home, and had tried to use them. The oversized bulbs were made for bigger fixtures (Outdoor lights mostly) and I was skeptical so I didn't even bother.
As far as a box goes, I'm not really sure how to make one.
What I ended up going with was actually an unfiltered UV reptile light found at a pet store. I looked on the box and it had a graph showing the wavelength of UV light and surprisingly it was in the right range, 350-420 Wavelength (nm). I was worried at first about the wattage being so low, but, I took a risk and purchased 6 of them, hung them above my screen, and it worked fine.
I hope this helps some.