The Custom General/NSView created by Apple for Safari’s Tab implementation.
Is it possible to find the source for this class?
No, just like you can’t get the source for any other Cocoa classes. –K
You can try code-dump. http://code-dump.sourceforge.net/ it won’t give you usable code. But you can figure out the implementation.
You’ll have to make your own, or see http://www.cocoadev.com/index.pl?General/SafarisTabBarView