The basic sticks are found at your local Lowes.  Ask them where the Driveway markers are. 

Really cool ones, and other stuff, are available with your swinkey: 

http://www.swinkey.com/

They are also available at most hardware stores and at Menards. Usually going in price for $1.19 to $1.59 each. A lot cheaper and not as expensive as the alignment sticks you buy from the dealers with their logo on them.