What is broken on it? Is it that the shift lever just moves freely without pulling any cable? If that's the case then you can most likely fix it. What happens is that the grease they used at the factory inside the shifter has gummed up from being old and the shifter not being used. That causes the pawls to stick open and the springs are not strong enough to return them to the ratcheted part. I've been successful using a pokey tool and some Tri-Flow to free the pawls of their sticky grease. My method requires that the cable remains in the shifter with it disconnected from the derailleur and the cable housing removed. Loosen the clamp so you can rotate the shifter upside down so that it is facing up. If the shifter has a cover that comes off, remove it. This makes it WAY easier. If the whole thing is going to come apart if you take the cover off then don't take it off. With your pokey, get those pawls moving again, back and forth, over and over and over. While you lightly tension the disconnected cable with your hand and start clicking the shifter around. Eventually, after doing this repeatedly, the pawls will start to return on their own again, catching the ratchet, and the shifter will work fine. New cable, housing, and end caps and you're golden.
Side note: My boss would hate it when I'd spend 30 min fixing some customers s***ty old shifter instead of just selling a new one. I always felt compelled to try anyway.
Hope this helps.
I dont have one because I put those dumb things where they belong.....the wastebin. 