AThere are plenty of tutorials on YouTube about making a topsy turvy cake. I refuse to buy pans that are unitaskers. I could be wrong, but I wouldn't spend money on new pans. Look around the Internet & you'll find out how to fairly easily carve it yourself. Good luck! :)
I have only made a couple topsy turvy cakes but I did learn (the hard way!) to use ganache under your fondant! Good luck!