Discovery and SideKick
The Discovery II and Discovery III did not come factory equipped with a power outlet for the SideKick, but there's an adapter kit that came out for the Discovery III that will also work with the Discovery II to add the necessary connection. I put one on my Discovery II. It's a pretty easy install. The adapter is a trapezoidal piece that fits where the wall cord plugs into the vacuum, and provides connections for both the wall cord and the cord for the SideKick, which is also included in the kit, along with a metal-tipped hose handle to replace the all-plastic one that would have come with the hose, and a set of straps to attach the cord to the hose. The adapter has a switch that turns the SideKick's side of the adapter on and off. It can get kind of confusing if the Sidekick you're using also has an on/off switch. I'm not sure whether they're still available through Aerus dealers, but they show up every now and then on eBay.