If your cool side is in the low 80s like that I'm not sure you need to stress about this at all. Your snake will move around to thermoregulate, as long as its eating and shedding well I don't know that you have anything to worry about.
Now if it really bothers you, what you could do instead of a CHE is use a smaller UTH to bump the heat up a little in the cool hide. Since that's your humid hide, I'd be a little concerned that even a lower wattage CHE might dry your moss up quicker than you'd like. What you can do instead is put a UTH on a thermostat on that side as well, and just turn it down to 76-79, somewhere in there.