You could run a small 12v pump (Bilge pump) off a car battery for quite a while
if you had a timer or cycled it on and off. You could get a small solar panel for it
too. Check westmarine... Buy you could probably get it cheaper...
Considering the thread's title, the DC to AC method sounded like an appropriate alternative if you already had a 120v pump. Although the efficiency may not be the best, you can say the same with solar panels as you just increased your exposure.
Needless to say, my 4.5gpm diaphragm pump runs efficiently off those 12v DC batteries. Well worth the $150 spent.