Suzuki sells a tool, around $35 to $40 I think. It has a hex wrench on each side. One side fits th busa and the other does not. It works well though, when putting the axel back on you can use a socket and torque wrench on the other end to get the proper torque on the front axel.
I bought the wrench for the busa and made one from an allen wrench (cut a 3" section off) for the front axel of my triumph.