For USB powered cool mist desktop humidifiers for tabletop setups, useful comparison points include placement, dimensions, power method, capacity, controls and the specific functions represented by the search.
Catalog options relevant to this combination include Compact USB Mini Air Humidifier, Mini USB Desk Humidifier with Night Light, and Mini USB Negative Ion Potted Air Humidifier. Their exact specifications can differ, so use the individual listings for final product details.