This http://www.homedepot.com/p/NDS-4-in-...4P05/100192743 + this http://www.webstaurantstore.com/dart...30116DN05.html or this if you need less http://www.webstaurantstore.com/dart...99916DN05.html
You can also buy a PVC pipe and cut it yourself.
PVC pipe with deli cups is nothing more than a water dish except it's disposable...not gonna help with humidity.