Adapter for Iphone to connect with Sony Dock

[canman]

One of the schools I teach at, went out and bought a bunch of Sony CD players with Bluetooth and a Walkman Dock. The sound is very good, and it is quite handy to use the Bluetooth function, but it just kills my Iphone battery. But I can't connect the Iphone, since it has a Sony Dock. I have looked on line to see if there is an adapter so I can charge my IPhone while using the Bluetooth function. Does anyone know if such a beast exists?

[Coligny]

Anything with a USB plug, plus all those external power pack...

Sony dock to even USB... Not so sure...