Thank you for bringing your questions here to Tundra Restaurant Supply.
Turns out, this locking mechanism is quite simple, and you may not even actually need a real key. This is just a sliding plate mechanism that secures the lid opening.
The little square hole atop the dispenser sits in a slot. The far right (as you are facing the device) is the locked position, and the far left is the unlock position.
You can certainly find something that can fit this square hole and slide it to the left, and press down on this left side where the hinge is located.
However, if you do wish to have a key, Tundra# 38124 may be the closest match. Unfortunately, the manufacturer does not make replacement keys for this particular model.
Answered on 5/31/2013 by Chris from Boulder