Fog Machine for tabletop gaming

I made this fog machine for my Halloween D&D session, and it turned out perfectly.
It gently mists out fog for 3-4 hours with the size of tank I made (which is as long as we play in a night) and is completely silent, not to mention it could fit inside a soda can.

The [module I used](https://www.amazon.com/gp/product/B00PAK245E/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1) is pretty standard and only cost me ten bucks, I'm sure it'll be comparably priced elsewhere

The lid has a cone so the water that hits it will drip back into the tank, and the tank itself has an external fill spot so you don't need to remove the lid to fill it.
Any 40mm fan will fit snugly into the lid, and I've found that the perfect amount of fog flow can be achieved thusly:

-12v 40mm case fan in the lid, powered by a 3.7v Lithium battery
-A square of index card taped over the fan with a 5mm hole in it.
It seems that any larger of a hole allows too much air through and the fog is too thin, but you