I bought the Driven brake guard that's inserted into the bar end. I have stock bars, so didn't have room for the Woodcraft style one. The Driven guard has a breakaway top, so in the event of a crash, your hand will slip out from the bar, but will protect from front or side contact from another rider.
http://www.rpmoto.ca/Lever-Guard-DXL1.htm
http://www.rpmoto.ca/Lever-Guard-DXL1.htm