The only way to get replacement vending machine keys is if you have the serial number for your lock and that lock's manufacturer is still in business. If this is the case, contact the manufacturer for information on acquiring a replacement. Unfortunately, due to the way vending machine locks are manufactured and sold, getting a replacement key is usually impossible and replacing the inaccessible lock with a working part requires destroying and removing the old lock with a drill.
In virtually all cases, vending machine manufacturers do not install locks on their machines at the factory. Once a soft drink manufacturer or vending company purchases the machine, they buy and install their own locks. Usually, when a reputable vendor resells the machine, he removes his lock, allowing the new owner to install her own lock. However, sometimes a seller leaves his lock in the machine. Without information about the lock's serial number or manufacturer, the new owner has no option but to destroy the lock to install a new one.
Drilling out a vending machine lock requires using a high-powered drill and two different drill bits. The person drilling the lock first drills a pilot hole using a smaller drill bit, then, using a larger drill bit, the person moves the drill in and out of the lock until the internal components are sufficiently ruined to remove the lock. Once the old lock is out, the new owner purchases and installs a new lock in the vending machine.