Dave the Tunze osmolators look nice, but pricey without the container.
I use plastic tote box type containers from Lowes, Home Depot, or The Container Store. Only cost about $10.
The ATO reservoir is seconday to making sure you like the equipment the ATO is composed of. The reservoir is only a plastic box anyways.
Having a pre-made reservoir like what you are looking at also sets up limitations as to what you can do regarding palcement, etc, whereas an ATO where you provide your own reservoir gives you more placement options.
The Tunze uses an infrared eye level sensor. Unique in the ATO market. Only one in the world like it. Ultra accurate, and Tunze has some of the best Customer Service in the world. I've met Roger Vitko, owner of Tunze USA at MACNA '08. Great guy.
There are many good ATOs out there, but the Osmolator is unique.
Dave