My favourite L bracket by far is by ProMedia Gear, but they seem hard to locate at the moment. Others may vary but I didn't have a good experience with a 'Chinese' one, didn't fit too well and had to be removed to access the battery holder, although the quality of the casting seemed OK, I just keep coming back to the would you trust your expensive camera body and lens to it?
Personally Having used Kirk before and still on one of my bodies that is what I would plump for...