Try Octopart. Link, Courtesy of 3V0.
**broken link removed**
Or perhaps if you have a substitute in mind you could share it with us, and we can tell you if it will work. I really do not think anyone wants to run through mountains of data sheets to find your sub without knowing what you do have. You get what I mean? What I am saying is I am sure there are many substitutes, but it could take lots of research to do.
It is like, well do you have a 2n2222, um no? how about a 2n3904 (Not that these parts are the sub) . We could go on for a long time. So what do you have as an alternate?