Harris Cyclery Brakes for Bicycles. I got my BR7301 Tektro 521AG Long-Reach Dual-Pivot Calipers from Harris no problem for just $50 and they only weight 350 grams. Not much given the cost.
I had assume my Trek 560 was long “reach”:http://sheldonbrown.com/gloss_r.html#reach with a “recessed”:http://sheldonbrown.com/gloss_r.html#recessed mount. But, interestingly, this is one of the few bikes I’ve seen with a short reach, but it is actually a modern one with a recessed mount and short reach. I didn’t realize the Trek’s of 1985 were so modern.