You can get those junction ferrules off of the top of the curved pipe that you find on V-brakes. Sometimes, the internal diameter of one side of it makes getting the cable housing into it pretty tight, but it can normally be done. I've done this as a temporary fix when I didn't have a full length of housing to replace one with, but then it worked flawlessly so it was quite some time before I actually got around to replacing it properly.

However, I wouldn't refer to them as training levers, and have never heard of that term before. Even many of the pro' cyclists use them in the Paris-Roubaix race, and in cyclocross they're almost universal. I find them particularly useful when in urban/busy areas, when I want to sit upright to see the traffic better but still have full control of the brakes. However, I no longer use them on my road bike, but I do have a pair on our tandem, where I want as much control as possible.