Portable air conditioner or dehumidifier?

Definitely not a dehumidifier, as these often resort to heating, or incidentally heat the room from which they remove the humidity. A high-end portable air con unit should do the trick, as some of them are equipped with humidify-dehumidify functions and a reservoir which they either fill or use depending on humidity levels. I don't know what marques you have there, but I know Whirlpool make one, we considered it before buying our window unit.