What Synchro said!
Tractor Supply Company has shackles for MUCH cheaper than anywhere I've seen.
They run about $11 for a 6 1/2 ton rated shackle. You can chose between screw in, or cotter-pin style. They are black already and the pin is usually a brass hue.
You can also get funky twisted shackles there for a little more.
http://www.tractorsupplyco.com is their website (though it's kinda hard to find anything on the site).