Cheapest place is usually on a cheap kmart wakeboard like a hydroslide. Otherwise, try ebay. In all honesty unless the board you got was really nice, you'll get a better board and bindings by just buying a leftover 2009 or 2010 package.
evo.com has some great deals in the outlet section. They're always running sale codes too that make it even cheaper. Craigslist or ebay are probably your best bets for used bindings. Whatever you go with, just be sure they are compatible with the board you have.
