I have five flash slaves for sale. The are very similar to the Firefly slave (sells for $58 + S&H) but have longer battery life and much longer range (1200+ meters). These are designed by the same person that designed the Firefly but I assemble them. They are $32 each with FREE SHIPPING 8) . I have used one of these units for two years and have not had any problems; I have not even needed to replace the battery!
Note: because of the wide range of connection preferences these units do not include a cord to connect to your flash. You will have to obtain your own cord, but soldering is NOT required to attach a cord. I only have five so when they are gone they are gone. If you have any questions, or would like to order one you can e-mail me at ryan13591@gmail.com.