If you are lucky there may be a number on either the ignition lock or seat lock. If there is take the number to the dealer and they should be able to make a key. Had a Suzuki GS850 nicked in the UK, bought another one with the insurance and needed a spare key cut. Dealer cut a new one using the number on the key, never asked for proof that I owned the bike. Noticed that the same key number was on the fuel cap lock. Anyone who wanted to nick it just needed to take that number to the dealer and they would happily cut a key for them.