KABASI Rabbit Cooling Pad, Hamster Cool Plate Ice Bed, Pet Cooling Mat for Bunny Puppy Kitten Guinea Pig Cat & Other Small Pets Stay Cool, Bite Resistance Aluminium Alloy Cool Pads, 12x8 in

Or you can get a metal rabbit cooling plate and stash it in the freezer and when you notice him by the vent get it out and set it on the floor. It's a lot less heavy than tiles. And cheaper too https://a.co/d/0fejZcMp