I expect there will be other, better answers from people more versed in Italian I@ stuff, but first off, Bonanno is, unless I missed something, still very much kicking around, so yes, he does have contemporaries, though most have less name recognition in the anglo world than him.
As far as whether or not he is the sole originator, it seems to me that Italian I@ is built on theory going back at least as far as Galleani. The connections being a focus on violent (and frequently armed) confrontation with the state, illegalism, and a generally uncompromising attitude.
I am hoping someone with a deeper knowledge of Italian anarchism (current and historic) has more to say on this.