Heatcraft sell a smallish one off the shelf over here.
depending on the size of your room it could do the trick.
Failing that, get your local sheet metal company to knock you up a stainless steel pan, put a defrost heater in it and control it with a thermostat and perhaps a fan to speed up evaporation and get rid of the water vapour.
You could also try controlling the heater with a float switch...
Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002