What kind of battery does the transmitter require?
Here is their recommendation from the Eggfinder support FAQ page:
We recommend using a 7.4V ("2S") LiPo battery, at least 300 mAH. You CAN use a smaller one, the Eggfinder TX draws about 70-100 mA when it's running, but that will reduce your operational time, of course. If you want to use a smaller battery we recommend that you power it up shortly before launch... mounting it in the nose cone or wrapped up in the body tube. usually makes that pretty easy to do.
I recently purchased a Turnigy Accucel - 6 charger from Hobbyking.com and it is simple to use and can charge multiple types of batteries including the LiPo's.