You can buy a single Ergotron DS100 triple mount and then use your normal built in stands for the bottom row. You MIGHT have to buy a longer pole (they are available) or simply buy a 24 or 36" in length 1.5" OD TUBE (not pipe) from say, onlinemetals.com.

It will not be black, but you could paint it, anodize it or have it powder coated.

Should be able to find one though.

Read my FAQ on this site for various mounting methods.