Update: I haven't tried all your suggestions yet, though gave kitty a paper bag that she was half interested in.
I brought kitty a catnip carrot, which is a very tough orange burlap-cloth-like carrot filled with catnip. She went completely wild! The first day, it was like she was an addict, glazed eyes, etc. Then the 2nd day, she was able to rip it open, so that was the end of that toy. It was catnip overload