Where to put plain object classes?

I do want an autoloader. That way, I can get rid of those 2000+ require/include statements and get to the actual coding.

Then write an autoloader! What can I say?

The original question is "what's the correct place to put a plain object class file?" and right now there's no way to load a class without creating a singleton and there's no autoloader in CI. That's why I use require and that's why I say that if the framework doesn't provide what you need, code it yourself.

This is turning into a debate on autoloaders...