put a "lid" or piece of glass/plexi/whatever on top of the screen cage and just aim the nozzle up into it. When you get tired of the "rain", turn your nozzle down and mist away.
my dome works kinda similar but i find it louder than just a nozzle, and mine kinda streams water instead of "rain". aquazamp did contact me and offer to fix it but we havent connected yet so cs with them is great.
its only $15 so it worth getting it just to satisfy your curiosity