Hi - I use one of the little travel neck pillows that are filled like bean bags. They are very light weight, and hold the Kindle up perfectly.
They work bed as well, where stands just topple over. Plus, when reading on your lap, they give a little extra height.
The one below is memory foam, but I use a lighter weight ones with little foam beads that I get at the airport.
http://www.amazon.com/Memory-Foam-Tr...0821245&sr=8-4