I actually was just talking about these on another forum and posted pics of my Lulu drinking the nectar portion of the diet.
Here you can see better how it's mounted on the cage. I can take the silo on and off without even opening the cage door.
Here is what it looks like from inside
The water silo is on the other side of the cage. I originally purchased green ones, because the cage was mostly in green. Then I decided to color-code the silos after I decided to serve the HPW in one. Yes, crazy, I know. I have yellow silos for the HPW and blue silos for the water. I went a little crazier than that and ended up with three of each color. Two yellows to alternate HPW, and two blues to alternate water, and an a extra set for travel. I change the mountings out on cage cleaning day. The green ones are just being stored as spares, lol.
I got them either at PetSmart or Petco, I don't remember, maybe some at both, they both sell that brand. They can also be purchased online.