When I posted this article, the world pretty much wiped out the inventory. http://cheesycam.com/quick-release-adapter-it-is-compatible-with-manfrotto/
Just FYI, if you haven't been able to get your hands on a Manfrotto Compatible Quick Release adapter, they are back in stock. They are perfect if you have the need to quickly move your camera from a Manfrotto tripod, over to another rig like a Slider, or Crane.
If you're just in need of the plate itself, they have that available too (again not stating Manfrotto Compatible)
Sliding Plate (not Manfrotto branded)