I replaced the entire plastic bracket and arm with a little aluminum piece securing the throttle lock almost invisibly to the starter/kill-switch housing. One end of the aluminum piece is screwed to the throttle lock, the other end to the start switch housing. So that requires a hole and threat in the housing, but that's easy to do. Eventually, it looks like the photo shows below:

To make this work you need to drill a hole into the starter-swith housing at the location you can see in the photo above. You may want to open the housing first and see for yourself where and how deep you want to drill. In my case I chose a chrome-plated 4mm screw ("'M4") which was 10mm long ("M4 x 10"). So, a 10mm deep hole would do the job. If you drill too deep you eventually drill into the starter switch - not a good idea. When you look at the inside of the open housing, you'll easily see what I mean.
To make an M4 thread you should use a ~3.3mm drill.

Once the hole is drilled you're ready to cut a thread into it. It's an easy task since the housing is aluminum and the thread cutter ("tap" as they call it) cuts through it like butter - just put a little bit of oil on the tool before you start. Then carefully and under a little pressure and back-and-forth (actually left-and-right) motion gradually cut the thread into the housing. Since you're guided by the 3.3mm hole, it's really easy. 
Finally, connect the aluminum piece with the M4 screrw to the housing and to the throttle lock at the other end. I used the original Allen screw (which was non-metric) and secured it with a self-locking nut (i.e., the kind that has a nylon liner). Very easy to assemble - and to take off should that be necessary. If you have everything you need, it's just a half-hour job. The end result is shown below - a nice and clean throttle lock, hardly notceable.

Now hop on the bike and test it out. See you on the road!
Hans