I've never seen one. Doesn't mean they don't exist. To work reliably, you need a fan to move the air across the media. Avoid at all costs those that spray a mist into the air that then evaporates as unless you use distilled water, you'll get a nasty mineral dust all over things that can be destructive to electronics and is a nuisance for everything else.
You could hook up a portable one to a water supply with a float valve to keep it full, but haven't investigated any to see if they are capable of being wall-hung.