Speaker power

I have these speakers that I like to plug into my mp3 player, but because of the size of the speaker, it kills my mp3 player battery. Does anyone know how I could hook up a power source (wall outlet, batteries, etc.) to the speaker so I dont go through batteries like crazy? Im more than willing to solder if need be.

Speakers

Some speakers have a plug to connect them directly to the mains, if you use that sort of speaker then it will mean that it won't have to drain the battery from the mp3 player.

The other option is to connect the mp3 player to the mains, if it has that option.