I have never used a fogger but think it might be overkill in that little tank. I would cover the same parts of the screen that you covers in foil with a damp cloth and then put the foil over the cloth.

Also a good way to help keep the humidity up in a problem tank is in its hides. Get moss(for sale at every pet store) and follow the directions. Take a protion and place a bedding in each hide. Also I find that misting the interior roof of the hide keeps a good amount of humidity within the hide. I do this during shed. The moss in the hide will create a microclimate and even though the tank humidity is not high it will be higher within the hide. This is not a fix to the problem but will help keep your snake healthy while you fix the problems since BP's are almost always in their hide.

You can then take the left over moss and place it around the tank floor. Then when you mist make sure to get it nice and damp and it will help raise your humidity.

If you continue to have problems you could move to a rubbmaid container, depending on your heat set up. They are great at holding humidity and you would have no problem finding one for a baby BP. We can cross that bridge if it comes to it. I hope this info can get you where it needs to be.