This might be a VERY doof answer Mitton, but bear with me.... I fell on my head!!
I have seen people using those automatic air fresheners and I believe you can get the canisters for a water option instead of the aromatic ones. Personally I havent tried looking for one, but you can set that to go off once a day so if you had to set it up against on of your vents my guess would be it would spray once a day into the cage. Worth having a look into. Once I get the big cages sorted for the retic and burms will look into on of those things.
I have also seen a fan that sprays a fine mist around the room to cool it off, might be a better option for those BIIIIGGGG constrictor cages and put it on a timer to go on once or twice a day for a 3 minute misting.