How much of it's tail is gone? If it's just the switch, that's pretty easy to replace, but if it's much more than that there's not much you can do...
Years ago, some of the show supply places sold replacement switches - not sure they do anymore, but you could check around. Maybe Nasco or someplace like that...
You can also go to a butcher and ask them to save you a switch or two. You'll have to leave a strip of hide so you can attach it with tail ties, and you'll want to spend a little time oiling and working that little strip of hide.
Another alternative is to take about 3' of sisal twine and unravel it. Just pull it apart until the strands are all thin, like hair (they'll still be loosely connected), then shape it with tail adhesive, paint it to match, poke a couple of tail ties through the top part of it and attach it to the tail...