Most filing cabinets are designed with safety features to keep anybody from bypassing the lock. This means you need a key replacement to get into the filing cabinet. It doesn't matter if you have a lateral or vertical file cabinet, replacing a lost file cabinet key isn't difficult.

If you still have a physical key, you should be able to get it duplicated from a local hardware store or locksmith. If you don't have a key to reference, then another option is knowing your key number to place a special order via a authorized distributor.