Search this site using this neat little function (found in the menu bar)
and you'll find loads of info on (ignition) keys, including whether your particular (European?) model might utilize an 'immobilizing' chip. Replacing a chipped key is more $$. Non-chipped keys can be copied for significantly less.
Update - got a spare key via: KeysInThePost
Cost around £12 delivered, just sent them a picture of the existing key and it was delivered recorded delivery a few days later. Key a little stiff in lock but starts the bike fine. The key is not a Suzuki blank but some awful looking thing, but is fine as a spare. There is no transponder to worry about.