Originally Posted by Paul L.
Incidentally if you want a really nice battery bag, Performance has some on sale (they are what they would call underseat bags). I used the longer variety and it will go upside under your top bar so the strap omes up around the bag and over your bar, then the seatpost strap can go around your headset tube. The one I got holds a 10 c cell battery pack quite nicely.
I got the following frame bag for around $10 shipped. It holds my spares and will hold the 5.5 lb SLA I use for lighting on some trips.
Nasbar frame bag