I've never seen these cases being offered for rent but you never know until you ask. It might behoove you to pick up a LifeProof case for your phone (or iPad) and use that instead. I realize it won't be nearly as satisfying as using your DSLR but it would save you a lot of coin.
And please tell me that Phuket is not pronounced like I think it's pronounced....
btw - welcome to Nikonites