Spotted this VW Transporter with evaporative coolers a few weeks ago.
And about a year ago I found an International 9200 fitted with an evaporative cooler at the sleeper (altough it also cooled the rest of the cab).
In this Volvo from the 80's can be seen both the evaporative unit and an auxiliary water tank.
workaround ideas to discuss among friends: Evaporative cooling: a low-budget yet energy-efficient way to improve thermal comfort in motor vehicles