I also recommend locksmith for key making because their prices are much reasonable than dealer.A locksmith may be able to make up a mechanical key from the lock. Then you may be able to turn the ignition on as your dealer requires. Maybe you can get the immobilser bypassed through an auto-locksmith?
Otherwise you are probably looking at keys, locks, ecu, and immobiliser change. Unless you can get a set from a scrappy and do the work yourself, your car may have to be scrapped as new parts and the work would likely exceed the value of a 98 Lantra..