I've become a big fan of
McMaster Carr. They sell just about ANYTHING you could ever want with respect to tools, fittings, fasteners, bolts, taps, etc etc etc. Excellent quality too. Hell, they just saved my butt when I picked up a 1 1/16" crowfoot wrench this weekend. And I may be getting a 7/8"-14 tap to fix a fitting...good luck finding those at Home Depot, Sears, or Lowes