My brother used to work for Fastenall, a company that supplies construction sites with nuts, bolts, and any fastener you can think of. He's into velodrome racing, and ordered a bunch of titanium nuts and bolts for his bikes. There should be listings in your local phone book under fasteners, nuts and bolts, or even industrial supply places.
Who knows, you could save an ounce and gain .00001HP at the wheel. ;D