Awww, Carl is adorable!
The cave bed is a Whisker City Pyramid Bed, and l found it at Petsmart. There were a lot of different colours and fabrics, but what l liked about this one was that it's soft and velour-ish.
The inner pillow that came with it is made of nylon, so the downside to that is that it creates a fair amount of static for the cats when they're moving around in it.
lt also has the nylon mouse-toy hanging in the doorway. l thought for sure that would be ripped off within a day, but it's all still in one piece