RS used to sell one of the Terks (HDTVi or HDTVa, I'm not sure). Haven't seen it at the one here in well over a year, though.
CC normally sells the Silver Sensor, and BB sells the HDTVa (and it's VERY overpriced there - so be prepared. Many people just try it from there and return it and buy it for nearly half the price online if it works well for them).