A lot of modern gear hisses. What gear is it? Can you turn down the tweeter? Reduce treble? In any case you will probably find the hiss is unnoticeable in a band situation-it's probably not as bad as you think it is, seriously.
There is no 'suppressor' that will cure this.
If you tell us your rig, how it is all connected, and how you have any processing like EQ, compression, or distortion set up, then we can make suggestions about how to reduce the hiss without a noise suppressor.
