There are a couple of options on this model.
First, there may be a key code on the lock itself, possibly an 8000 series number for a regular key or a 1000 for a round pin style. If you can read a key number off the lock then you might be able to use that number to order a replacement key through Waterloo Toolbox at 800-833-4418.
If not, you might be able to reach the actuator that releases the lock on the drawers. You would need something fairly slim and long. If you check the parts diagram for this model online at Sears Parts you can see that the lock turns an actuator rod, reference key number 12 in the diagram, which moves the actuator channel, key 11, at the back of the drawers. If you can reach between the top of the frame and the top drawer and move that actuator channel to the right or left then you might be able to get at least one of the drawers unlocked. With the drawers out you can reach the horseshoe shaped clip that holds the lock in place and then remove it.
If neither of those options work, you will need to drill out the old lock until enough material is removed to get it freed from the toolbox frame. Take it slow and be careful so that you do not remove material from the frame itself that might be needed to hold the replacement lock or horseshoe clip in place.
The links below have additional information that might also help.