Can a more powerful battery be installed?

Hi. I mainly use my iPod Touch 3G 32 GB for running backing tracks that I produce in GarageBand, then load them as Playlists into the iPod. I want to be able to run the iPod at least 3-4 hours without recharging, but I run out of juice before the gig is over. Is there a super, more powerful internal battery available that I could install that would last longer? Also, what are any recommendations for external battery packs for this model iPod Touch that I could buy as a backup system?

Thanks for any advice. Steve