If you are looking for a DSLR top light, I would highly recommend the Tecpro Fellini Click LED Camera light. It is very lightweight but has some serious power. The light has a dimmer switch so you can get the right amount of light you need.
It also comes with coloured panels which magnetically clip on, so you can easily change the light from daylight to tungsten. It has a ball and socket head, which will fit on the hot shoe on top of your 7d or 5d C300 etc.
The magnetic colour panels are really sturdy, and being able to clip them on to the edge of the light is pretty useful for run and gun shoots, if you find yourself moving from day light to tungsten situations.
For power you can either run if off 5AA batteries or you can attach an old Sony video battery (any of the following LF570, F770, F970 ,F550,F750). You can also attach several of them together to create a panel.
As you can see from the photos above, it is fairly rugged in construction, way more so than most LED top lights.
There are certainly cheaper LED top lights on the market, which I have used but the build quality isn't as good. The fact that the Felini click has magnets on the edges of the defusion and tungsten screens makes the light really quick and easy to use.
I used this the other night on a shoot for the BBC. The presenter was sitting in a car, and needed to be lit gently enough so it was still possible to see the small amount of light in the street as well as the presenter. The Fellini click was perfect for this, I could just set my exposure to capture a small amount of the scene through the window and then dial in enough light so the presenter was well lit.
If you want to buy one from the UK I bought mine here.
Another popluar LED top light is Litepanels LP-Micro. These guys are the market leaders when it comes to LED light panels so I expected their top lights to be of a similar quality, however, this is not the case. The light is really light weight and feels fragile. You get the sense that after a few tough shoots it would easily break. Another big issue with it is the thin plastic defusion and gel covers, these have to be slotted onto the front of the light, which is a bit fiddly and would probably be damaged after frequent use.
With regards to power, I haven't tested them side by side, but if you look at the difference in the number of LED lights they have, it is easy to see where the power is.
The two lights are a similar price, in fact the Tecpro Fellini Click is slightly cheaper, but as you can see from the photos Tecpro is way better built, and is a far better buy in my opinion.