there's a service on line that will fix this for you
you pull your TWICE, send it to them with your VIN. They get a new key cut based on the VIN and program up the TWICE to accept it.
something like lostsaabkeys.com
Saves you from having to replace the cylinders in the door, ignition and trunk (if you have one there) and the trip to the Tech II to get a new.used TWICE married.
But this isn't cheap.
If you have access to a Tech II you can often find a bundle on ebay with a TWICE, ignition module and at least one key. A cheaper option by far but more work. What I'd consider doing there is to get the TWICE with key and then order two keys for your VIN from thesaabsite.com and two remote guts from ebay. Take the lock cylinder out, use a screwdriver to turn the ignition to on, marry the twice, use the key you bought with the twice to get into the system and then program the two new keys back into the system then put the original lock cylinder back in. That way it matches the VIN if you ever have to order another key and you don't have to change the door/trunk locks.