A lock with the key over ride is a must when there in only one entrance/exit. Without the combination there is no way to know if the lock is operating properly.Combination it is a very involved process to reset the lock to accept a new combination. Back be removed, the lock disassembled, the combination chamber removed and the tumblers reset. FYI, if they don't have the keys a locksmith can not just make a key.
The over ride lock core will have to. The item "Kaba LLP1020 Pushbutton Lock Panic Bar Exit Device withOver Ride Core & Keys" is in sale since Monday, September 04, 2017. This item is in the category "Business & Industrial\Construction\Building Materials & Supplies\Doors & Fixtures\Locks & Locksets". The seller is "bake98" and is located in Oxford, Pennsylvania.This item can be shipped to United States.