A couple of us here have done retrofits of the SSII on our JS700 guitars. I believe that the only bridge that will directly fit is the Ibanez Gibraltar III used on the SZ series. BUT, those are a string-through-body-design, so you have to drill holes through the body and install string ferrules on both sides of the body. I did quite a bit of checking before I did the conversion, and as best I could tell, no other bridges (Tonepros, Gotoh, etc.) would fit the SSII stud spacing. There are undoubtedly other bridges out there that I didn't check into, but my guess is that (unlike Ibanez) most aftermarket bridges will conform to the industry standard stud spacing. (Those dimensions can be found at the Stewart-Macdonald or TonePros sites).
Bert
Bert