Connecting a speaker circuit to a rechargeable battery pack

[orushton]

I've designed, for A-level, an iPod dock but i need some help with the electronics. I have a small amplifier circuit (from my GCSE electronics course) connected to a speaker which is at the moment powered by a standard 9V battery. I was wondering if anyone knows how to replace it with a rechargeable battery pack. I understand I will need a plug with transformer and a rechargeable battery pack and internal/integrated charger but am not sure where to get the components from and how to arrange them. Any help really appreciated. 

[audioguru]

A rechargeable 9V little Ni-MH battery can power an amplifier for a short duration.
A battery charger IC can be used to make a charger for it.
The IC limits the current then shuts off when it detects a full charge.

I have a VU meter that has a Ni-MH 9V battery in it for portable use. It is simply being continuously trickle-charged with a low current.