I'll second your advice on this much - don't do illegal things, especially in a foreign country. You're talking to a guy who doesn't smoke in JA and declared coffee and spices when coming back into the US my first trip - because I didn't know for sure whether you had to or not. I am one who believes in following the rules - but also in taking advantage of flaws in the rules. Note I am not saying break the rules, I am saying follow them to the letter - so strictly to the letter that they actually benefit you.
In JA they have red tape and rules that are insane. When you think about it - these rules are almost comical. In this case we are talking about, it's not what is in your baggage that determines whether it is declarable, it's what is in your head. Since if you intend to return with it, it's your personal possession and there is no duty. But the exact same item, if you intend to gift it - you should declare it and pay duty. So I say don't lie about a reason - just truly change your reason. Nothing says you can't change your mind later. That's why I think this is insane.
So I admit I could have expanded on my reply - like I tried in the 2nd post - and what I said just above. I could have said explicitly I was telling the OP to change his mind on why he was bringing it down - since that's all it takes to be able to be within the rules. But I took a short cut in saying what is the same thing - if you read my exact words - so I'll take my lumps. Everyting criss, mon.
But that might only go as far as living with yourself about being a good person. I also agree if your item is found, you might have a hard time convincing the customs guy you're being honest it's your personal item. I don't know what they do in that case - do you pay duty and keep your paperwork, then collect a refund when you leave the island taking the item with you, proving to them you were telling the truth all along? Doubtful.