Talk to Timsons (key cutting folk in a shopping centre near you). If you have the red key system they'll be able to cut and program for you, if you have a 2 on the (usually) blue keys, they should be able to cut you an uncoded copy of the other key, you can then (carefully!) remove the plastic bitfrom the other key (contains the code) and glue it onto the new key. Operations involving FIAT and keys are often expensive............