I think @YARNLADY has a good point, those inverters are great, that way instead of buying a different DC adapter for every single electronic device you have, you can buy one inverter and plug ANYTHING into it that you can plug into a wall. I’m not sure what they cost, but I know I have 2 of them and I found them both for under $20, which is probably on the low end, but not impossible.
The other thing I might suggest, and I don’t have an iPod, but I do have a Zune and one thing I know I always do if I want my battery to last for a long time is to change the settings so the screen goes blank after 5 seconds. Then as long as I don’t touch it, since the screen is what uses more power than anything, I can play it for a very, very long time. Also, I looked at the specs online for the iPod touch, and it says the battery life on a full charge will last up to 30 hours of audio or 6 hours of video, so that pretty much says what I was saying, if you have the video screen on, it uses 5 times as much power, makes sense based on my experience with the Zune. Now these are maximum ever recorded with a brand new, fully charged battery, probably with the volume down, and definitely with the screen off. I’d say as long as you keep the screen off “most” of the time, and fully charge your battery beforehand, you should be able to last for 2 hours, I mean 30 is almost definitely an exaggeration, but not so much that you shouldn’t be able to get 2.
Now, if in your experience you are using your iPod without turning the screen on and you’re NOT getting 2 hours play time, I’m going to suggest that perhaps your battery is dying and it needs to be serviced.