i would be very difficult to get a pan for the feisty ferret beause only one door opens up.
i have had one for many years and right now Chewy is housed in it. when i was petsitting a few months ago i put a very heavy 12 x 12 marble tile over a piece of fleece to cover the hole. the chins cant move the tile. you could also get a piece of sheet metal to cover over the hole if you are trying to split the cage but the tile is way heavier.
if you are just trying to keep the poop 7 hay in, since there is a slide out tray on the bottom, i just use fleece and whatever falls thru i empty out the tray. i also custom cut fleece to fit the upper level so he can run up & down.