I've been looking as well and so far all I've found is the Vista cruise.
http://goo.gl/hA27n
I had one on my GS and it worked fine.
But for the ST it's going to need some modifications and drilling which I'm unsure of.
The Throttlemeister won't work as is either. It comes with a bar end insert which it screws into. This might be adaptable to the existing plastic insert that holds the throttle return spring in place. Might be as simple as using a different bolt and discarding the insert Throttlemeister provides.
Take a look at the pictures here
http://goo.gl/dVzE0 for ideas.