I suggest going to eBay. I was able to find additional keys for my 2816. I knew the code off the key and managed to find them. I agree with what a previous post mentioned. More of a safety feature than security.
I am guessing the key switch on your tractor might have a code some where on it. If you can take it out and look you might be able to get new keys from either the dealer or an eBay search. Just a thought. Hope all works out for you.