Honestly, not sure if there is any. Even though i am not really sure, but if there is. I would be illegal IF i am not mistaken. Since you can just change the AMXX files of... lets say, EVM in to SMA source files, and then you can simple create your own.
Yeah, I'm with Skyrider on this one. I'll close this thread, and if another Mod or member knows if this is okay, they can PM me and I'll open it back up again.
Edit: Turns out AMXX plugins must obey the GNU General Public License unless they talk to the developers of AMXX. Since we don't know whether or not that has occurred, this thread will remained closed. If you want the source code for any plugins, you'll have to contact the makers of said plugins and take it up with them. sorry.