Living in the AZ desert myself, I feel your pain. Here's the humidifier I run in my snake room (hooked up to a Spyder Robotics hygrometer): http://www.laskoproducts.com/9-0-gal...er-model-1128/.
I've been running it for the past several years without issue (always keeping up on preventative maintenance and using DI water to avoid mineral build-up). If you have any questions, feel free to ask!
Best regards,
Eric