The first Shimano brakes Jeff linked to are Tiagra level (4XX series) components but will work every bit as well as 105 or Ultegra at significantly less cost. The second link shows brakes that the Universal Cycles site says are "Sora" but the series number (6XX) and the price suggests they are Ultegra level. Both are "long reach" (47 - 57 mm) designs in the modern idiom.

Now, when you say you need a longer brake reach, how long do you really need? These days "short reach" brakes (37-47 mm) calipers are by far the most common and "long reach" (47 - 57 mm) are still available, as Jeff noted above, and used on light touring and other less-racy types of road bikes. You mentioned Tektro 559 calipers and these are VERY long reach (55 -73 mm). If you really need that much reach, Shimano doesn't make anything that long and there is no way to adapt any Shimano brakes to this use.

As noted, Tektro does indeed make fine brakes and they are OEM on a lot of otherwise quite expensive bikes. Keep in mind that if you really need calipers as long as the Tektro 559, the braking power, i.e. the hand effort needed to achieve a given braking level, will be higher than any shorter reach brake since their leverage isn't as good. It's not a fault of Tektro but inherent in the design.