Crane humidifiers
Crane has 2 units here, from $50 to $70, across one type. The most capable is the Crane Drop EE-5301 at 1 gal/day, enough for 246 sq ft. 0 of the 2 cannot produce white dust.
Across the lineup, Crane's published room sizes average 2.0× what the output supports, so treat the square footage on the carton as a ceiling rather than a rating. How that is calculated.

Crane
Crane Drop EE-5301
The teardrop shape has been on nursery shelves for over a decade and is probably the most recognisable humidifier in America. A gallon of water, twenty-four hours, no filters, and a tank moulded from antimicrobial plastic - Crane's answer to the pink-slime problem, and a partial one, since the material inhibits growth on the tank wall rather than in the water. Crane's own documentation is inconsistent about what it covers: 500 sq ft on most retail listings, 250 in one of its spec sheets. The arithmetic supports the smaller figure.
246 sq ft supported · box says 500 sq ft

Crane's fix for the original Drop's two real problems - the bottom-fill tank and the neck you could not get a hand into - plus a sound machine and a colour-changing nightlight aimed squarely at nurseries. The top opening is wide enough to reach inside and scrub, which is the single most useful change and the reason to pay $20 more. Three sleep sounds, an aroma tray for vapour pads, and the same one-gallon, twenty-four-hour, no-filter arrangement underneath.
246 sq ft supported · box says 500 sq ft