Humidity control for small spaces???

[Donald R. Guthrie]

I need some misting device / humidity control for a small growing chamber
(about 40 cu. ft).  I was using an old ultrasonic Bionaire household
humidifier until it died.  All the similar devices available here in
Vancouver seem to be the "wet towel/fan/water pail" variety that do not get
the humidity much over 50%.  Does anyone know of a readily available
ultrasonic unit , hopefully at a reasonable price.  Alternatively, can
anyone suggest any other modestly priced alternative?   I appreciate your
help.
Thanks,