Thanks Calvin!
The fan is just a plain 5V case fan, but it's a large, noisy one! One problem I forgot to mention in my original post is that the old fan pushed so much air that there was a lot of air exchange with the outside through the cracks, and the humidity drops from 80% to under 60% within an hour or so.
The new fan is not waterproof, but it's rated to 80% humidity so I'm crossing my fingers. The new fan is also much smaller and lower airflow, which should help with the small enclosure and air leaks.
I forgot to mention my (temporary?) solution to the fogger splashing. I took a 20oz. soda bottle, cut the top off, used a Dremel tool to cut/melt holes in the side, and then inverted it over the fogger. You can see the bottle sticking up out of the sour cream container on the left side of the tank. The main problem with the bottle is that it's so light that the cord from the fogger tends to push it out of position. I still get a little bit of splash outside of the container, but it's not a big deal.
Kelly's Korner Orchid Supplies sells an umbrella for the ultrasonic foggers for about $5. I'll probably break down and buy one eventually.
Kelley's Korner Orchid Supplies
Bryan