I'm afraid I don't really know much about casting to make a copy or a kit, this is just a one off that I made for my wife. If I figure out how to make copies I will definitely let you know. I don't suppose you know any companies that do castings/kits?
Actually it's super easy to do! I don't know of businesses or people whom do it professionally but I do know alot of professional sculptors do have people that do it for them! People like me and many other artist though cast their own sculpts. There's LOTS of videos on YouTube on how to do it. You can buy the materials off of eBay or amazon. I would say hobby lobby but that's way more expensive. I would advise the RTV rubber silicone molds. The high strength stuff. If your wanting to mold and cast your own stuff.
Thank you very much, I had the privilege of swimming with Whale sharks at the Ningaloo reef in Australia and I must say it was one of the best day's of my life, so I would totally recommend it. I done the sculpture as a gift to my wife to remember the day and because they are such beautiful creatures.