First of all I take old usb fan and try using it. But I discovered that it was too fast for this purpose. So I replaced it with brushless pc fan. It give perfect results.
Step 2: Preparing The Enclosure and Assemble Everything
I marked fan and switch on the box then I cut them with rotary tool. Then hot glued everything into the box and also hot glued bunch of magnets for water resistance . Next I painted the fan (Just looks good).
Step 3: Results (You can see better results in 2nd video)