As far as I know, they were supplied as original equipment. My truck has one. They were probably stored under the seat. Some sort of padding would be good if you're going to do that. 70 years of rattling around under there might wear a hole thru the floor, helping the rust do that. I have no idea if new ones are available. If you really want one (potential arm breaker), I could measure mine and take some photos for you.
They aren't listed in the Vehicle Info Kit as standard equipment or options, but neither is the tool kit that was provided with each truck.
