From the times I’ve used this “solution”, I had access to a commercial ice machine at the building in question. I think if you want good cooling for an 8 hour work day you probably need 10 gallons of ice. I.e. a 5 gallon bucket filled with ice, times 2.
Commercial ice maker that isn’t much problem, but for someone without a relatively robust home ice maker it can be a little hard to easily produce that much.