Im not sure if this would work but just an idea. I checked out the cat carrier you posted and when I did the cm to inch coversion it came out to 13 inches wide and 13.8 inches tall. Since the wheel itself is about 12 inches would it work if you took it off its base and drilled a hole in the back of the carrier to attach it directly to it. That way you could take it out while traveling for safety but you could attach it every night to let him play. I think you could do it if you got two really big washers and a wing nut, if yours is on the base you might beable to use that hardware.