Coolidor question!

[gomeitsmybday]

Hey everyone!

So I've been enjoying my Coleman 120 quart coolers (3 total) functioning as my stash for long term aging humidors. I've had a few hiccups along the way (had to seal the spouts, and one required some weather stripping which works great btw) but generally speaking they have served me well.
However, I've noticed lately that by using 2 separate wifi (remote) hygrometers that the bottom of the coolidors often has a much higher rh than the top region. As much as an entire 1% difference.

Now...I've already done some preliminary research and found that some people recommend using a small battery powered fan to circulate the air within the coolidor which is a swell idea imo but there is a problem. Most people are recommending the Oust air freshener fan and it appears they have been discontinued for some time now.

I've actually even taken it upon myself to rig up some computer fans to a battery which worked great initially, but managed to completely drain the battery in a matter of days. I've considered trying to research and find a way to rig a timer to the fan & battery but my electrical engineering knowledge is limited at best.

So with all of that said, do any of you use fans in your coolidors/humidors? If so what fan do you use? Ideally looking for an affordable option but really open to any suggestion. Or, alternately, do you think that a 1% difference in rh within areas of s coolidor is fine? Thanks in advance for any and all suggestions and feedback!!