There are
collapsible water containers that should fit in your cat's carrier and can be left filled during the flight.
Not exact matches
Collapsible bowls, soft foldable bowls, receptacles that clip onto human
water bottles and many other types of drinking
containers are available at pet supply stores.
Travel Bowls for dogs including the To Go Bowl travel dog bowl,
collapsible bowls, portable drinking
containers, stainless steel
water bottle for dogs, doggy lunch boxes and more!