Lost Key

I lost one of the keys to my 2002 Cabrio. what is the cheepist way to replace this key? Do I have to go to the dealer.
Thanks

Hey im sorry to tell you that you have to go to the dealer...atleast for the programming...you can buy a key somewhere else as long as you get the right kind (i.e. ebay) but its like a $50.00 charge to get programmed