Go to a hardware store, get a wallpaper steamer and a big Rubbermaid bin / trashcan or a food grade barrel. Cut a hole in the bottom on the bin to attach the hose from the steamer. Super easy, I built one a few years ago and I am not handy at all. The guys at the hardware store helped me get all the connectors and everything once I explained what I was making.
Not as good as the 2k ones but it worked great for me for me when my pony was having allergy issues.