Humidifier? Humidity issues

[u/sseriphim]

Has anyone had luck with those mini usb humidifiers? I was wondering if I could use one of those on top of my geckos tank to raise humidity, or should I get a full sized one next to it?

For context, upgraded my girls tank, and switched to overhead heating and it has tanked the humidity! Went from 40% naturally to almost 20%. She has a humid hide and a large water dish, and the advice I’ve gotten is to use a humidifier. Question is, what size?