A 12v-110/60 inverter and a 12v battery pack will do you. Radio Shack or an auto parts store.
Or even easier, work out what DC voltage the unit runs at and run it directly from a battery pack. No point inverting 12v up to 110v only to have the internal transformer and rectifier convert it back to 12v again!
EDIT: More likely 24v.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.