I'm amazed you remember the name of the cat and the aunt,
flicrat! (Kissemisse = Pussycat BTW.)
I don't know the book but IF the author is Swedish(?) you might be able to find it again with the help of
The Swedish Institute for Children's Books. As you can see they're closed for the summer but do get in touch with them when they open again. It won't be for sale there of course but who knows, they may agree to copy it for you if you're willing to pay? I'll help if I can, just post a FAO swedeheart in this category and I'll probably see it.