Where can one purchase a Petsafe dog collar?

Wireless Dog Fences create a circular boundary around a central base station using radio waves. They are quick to set up, but are not yet anywhere near as good as in-ground (wired) dog fences. The units have a lot of trouble going through obstacles, particularly a metal roof, siding, trees, and some walls. They are also imprecise, with even the best system, the boundary will move 3-5 feet second-to-second. The units can also be slow to respond, meaning the dog can get the correction too late and can keep getting the correction for a few seconds after they return.