I ordered from UK. They were very nice and the order arrived promptly.
I do find that the ones I got (the kit that you insert in your own bucket) tend to drip. I keep a shallow bucket or tray under mine, weighted with a rock. I haven't set up the ballcock system yet -- that will happen when the permanent coop is built, soon. For now I just fill the bucket every day or two.
We built a trough watering system that constantly recirculates water from a 55 gallon water drum so that the water is always moving. I believe it's healthier to drink moving (non-stagnant) water