Can I use a SRAM Powerlink on a Shimano chain Have 9 speed Shimano chain that I need to shorten.   

I don't have the Shimano pin so I need to go buy one.
Could just reuse the regular pin but I already broke one chain tool trying that.

I think the SRAM Powerlink would be more convenient.     

Is it safe to use the SRAM Powerlink on a Shimano chain?
Or is there some other reusable connector (master link) for a Shimano chain?
As long as it's a 9-speed power-link, you can. I have chains in all bikes connected this way and find it most convenient method. The one made by SRAM is also the easiest to open.