If you are feeling ambitious, you can make them yourself...you can make a set of three for just a little more than you can buy one winger with electronics....
Mine will work around 120 yards, which is plenty for my purposes. If that fits your purposes, see the thread posted above. I put a bunch of diagrams on page 2 of that thread....I made a set for myself and also a set for a club member...no complaints from either of us so far. But again, if you are planning on running marks farther than about 120 yards, you may have to get the upgraded version of electronics (which they do sell).
Regardless of the route you take, happy training. If you decide to go DIY route, please dont hesitate to ask me questions.