The run of the mill computer fan, 60mm or 80mm is just fine.
It runs on a maximum of 12volts. If you use a cell phone charger it will run typically at 5v output which will calmly turn those fans. If you find a charger/adaptor at 8volts, it will turn faster and move air more aggressively.
If you run it at its maximum with a 12vout output charger, it will typically be noisy but will really create a hurricane of air movement.
Amazon.com has plenty of 12v and 120v fans to choose from. I ordered my two from amazon and of course I ordered 2 in case the one craps out. I ordered a 120v just so I can wire it in to come on when my light bulb comes on.
I did not want to mess with the 12v and having to use a 12 adapter. My fan moves a lot of air, but it works and works well.
I can not remember what kind it was.....hmmm let me check.
AC115V Speed = 2600
Double Ball Bearing
I am sure I could use another kind or another voltage, but it works for my needs.