BATTERY PACK for Projector

Hey
I'm wanting to hire/buy a battery pack solution to run a digital projector away from mains plug...for at least an hour
Can anyone suggest anything?
Looking at Car batteries with an inverter...but they will be very heavy...
Not interested in a generator...
I'm sure others have fantasies of projecting on trees, grassy fields...lol

golf buggy batteries.
dont use car batteries, they aren't made for it.
there were a few threads on vjforums about this..