beano - boo, hiss.
ivan, in the event that this is a serious post ...
You cannot filter moisture out of cold air. A water molecule is small than a nitrogen or oxygen molecule.
You can heat the air which will reduce its relative humidity, but then you lose cooling capacity. You can remove moisture chemically by running it through a desiccating agent but that is a short term process. You can remove moisture mechanically by using a dehumidifier.
If you want cheap, my suggestion is to recycle an old case or simply do without:http://www.tomshardware.com/forum/262730-31-breadboarding