Where can I get a "Beeper" watch?

I have read somewhere of some people using “beeper” watches, that beep on pre-set interval times, and was interesting where online I could get one. Does anyone here know of a quality watch that does that?

Also, on another note, Clyde Hart is said to use these watches. The question I have on him is, that I would like to get an up to date training program he uses. I know there is one out there, but its from the 1970s. Any information on what he is doing now, or close to now?