You can't unlock the 4S without a Gevey SIM or an IMEI unlock. Jailbroken or not, that doesn't affect the 4S' ability to be unlocked or not. Only the iPhone 4 on baseband 01.59.00 and any iPhone before it are capable of being unlocked after being jailbroken. You can still buy the IMEI unlock for the 4S wherever you are, since all that counts is the phone's origin and what type it is.