Earlier I posted about how you can use a rotating flash bracket to add an extra hotshoe to your camera. The rotating flash bracket is nice, because it acts like somewhat of a half DSLR cage, but here's another option. This dual bracket mounts to the top of your Canon EOS 5D Mark II or Canon 7D. Not sure if I would put this type of weight onto a 550D / T2i, but that's your decision. Available through the links below.
Click image to purchase from BHPHOTOVIDEO.com
Photo Video Dual V Bracket for Video Lights & Microphone at B&H
Other version is half price via Amazon
Photo Video Dual V Bracket for Video Lights & Microphone